When Malcolm X went to Jedda in the early 1960s, he was shocked by his reception. Back home he was a pariah - a race-baiter and white hater - who would become even more loathed by the US authorities when he returned to preach not racial segregation but socialism. In Mecca it was a very different story. A senior Sudanese official hugged him and declared, "You champion the American black people!" An Indian official wept, declaring "[his compassion] for my brothers in your land". In his autobiography, Malcolm X wrote: "The American Negro has no conception of the hundreds of millions of other non-whites' concern for him: he has no conception of their feeling of brotherhood for and with him."

When US Secretary of state Colin Powell addressed the earth summit in Johannesburg in September, he was greeted not in a spirit of brotherhood but with a barrage of booing. A year earlier, at the anti-racism summit where Powell had refused to show up and the US resisted all talk of reparations for slavery, the cartoonist for the South African newspaper Citizen ridiculed him: "Coming Uncle Tom?" ask two characters representing participants at the conference. "De Massa in de big house says I ain't," responds a Powell dressed up as a house servant. Given that Powell is one of the most liberal figures in the Bush administration, one might only imagine what views are reserved for his African-American colleague Condoleeza Rice, the hardline hawk with the president's ear, his chief adviser on international affairs.

There was a time when the rest of the world looked at black America and saw dissidence. They stood on Olympic podiums victorious and rebellious, saluting their national anthem with a clenched fist. In 1960, a year after the Cuban revolution, Fidel Castro left the Shelburne hotel in Manhattan after they demanded that he pay his bill in advance, and headed for the Teresa Hotel in Harlem to a hero's welcome.

But not any more. Thanks to shifts, both subtle and seismic, in class, politics and culture, black America is now presenting a radically different face to the world. Today, they offer the developing world the official policy of one of the most reactionary US administrations in recent times. Where its singers once railed against the affliction of being raised in the ghetto, now they trumpet the aspirations of life among the ghetto-fabulous. Where its sports personalities once reigned in boxing, now they are masters at golf. And whereas they were once hailed in Africa, now they are heckled.

Such observations come in the form of a description, rather than a criticism. Black America's ascent to such positions of power and prominence in areas where they now find themselves blamed for some of the ills that their nation visits on the world is, on one level, a mark of success. Their status as second-class citizens was an emblem for the global oppressed. It was a view that was rooted in politics, but which extended to culture and sport, too. In a 1927 poem, the fledgling Soviet Union's poet laureate, Vladimir Mayakovsky, wrote: "If I were a Negro/I would learn Russian/just because/Lenin spoke it." Years later, nationalists in Northern Ireland adopted civil rights songs as they marched through West Belfast, while Angola's newspaper, Diario de Buanda, lamented "the tragedy of Negro life in America" after the Freedom Riders were bombed in Alabama.

But this solidarity stemmed as much from black America's position of weakness as from its culture of resistance. Much of the world identified with them because they, too, were deprived of basic rights. For a brief moment during the 1960s, the demands of Black America chimed with those of colonial Africa and Asia - everyone was fighting for the right to vote. Shortly after Kwame Nkrumah was elected the leader of a newly-independent Ghana, he invited black American intellectual WEB DuBois to edit an Encylcopedia Africana and Paul Robeson to assume the chair of music and drama at Accra university.

But once those rights were won, the paths diverged. Black Americans lived in one of the most powerful nations of the world; Africans and Asians in two of the poorest continents. One of the first institutions to be integrated was the military, thereby sending black Americans to the frontline of incursions across the globe. As the focus shifted from civil rights to economic rights, so a handful of African-Americans slowly started to seek to protect their economic interests and align themselves, albeit tentatively, with the right. Equality of opportunities, in short, earned black Americans the chance to be every bit as reactionary and imperialist as their white countrymen.

So long as those rights were honoured in principle but breached in practice, those opportunities were fairly rare. Riots that raged through America's northern cities during the late 1960s, the rise of the Black Power movement and the assassinations of Martin Luther King and Malcolm X kept the plight of black America firmly in the spotlight. In a world with two superpowers, where allegiances were often based on the principal that, in times of crisis, the enemy of my enemy is my friend, black America had lots of friends because America had plenty of enemies. In postwar Paris, antagonism to US political hegemony found expression in the support for the growing number of black artists in the city: "Opposition to the racism of the United States was reinforced by the political climate of anti-Americanism," writes Tyler Stovall in Paris, Noir: African-Americans In The City Of Light. "The Parisino Left now regarded Americans as a symbol of ideological consciousness."

Black Americans had, in effect, gained exemption from criticisms of US foreign policy abroad, because they were considered victims of the same repressive regime at home. This was true even for the few who became official representatives of the US abroad. Ralph Bunche, who negotiated a truce between Arabs and Jews in 1947 and later went on to become the United Nations' under-secretary for political affairs, became the first black American to be awarded the Nobel Peace Prize. Andrew Young had been America's first black ambassador to the UN, albeit under a Carter administration that pursued the most liberal foreign policy since the war, before he was forced to resign for holding informal talks with PLO representatives.

An impression created by black American intellectuals and articulated by politicians found its most potent expression in popular culture and sport. There was an organic connection between black artists and performers and the aspirations of African-Americans. Their lyrics provided a soundtrack for the politics of the day that resonated beyond North America. Early in 1968, Aretha Franklin appeared on a platform with Martin Luther King. A month after he was murdered, Think was released - a love song and a warning to white America: "You better think, think about what you're trying to do to me/Yeah, think let your mind go, let yourself be free/You need me and I need you/Without each other there ain't nothing people can do," and then the rallying cry "Freedom".

In sport, there was Wimbledon tennis champion and human rights activist Arthur Ashe. But largest and loudest of them all, on the world stage, was Muhammad Ali. "We knew Muhammad Ali as a boxer, but more importantly for his political stance," says Zairean musician Malik Bowens in the film When We Were Kings. "When we saw that America was at war with a third world country in Vietnam, and one of the children of the US said, 'Me? You want me to fight against Vietcong?' It was extraordinary that in America someone could have taken such a position at that time. He may have lost his title. He may have lost millions of dollars. But that's where he gained the esteem of millions of Africans."

Precisely at what point black America stopped giving this impression to the rest of the world is not clear. Up until the late 1980s, rap groups such as Public Enemy still vowed to Fight The Power, Tracy Chapman was talkin' 'bout a revolution and Gil Scott Heron linked the oppression of blacks in South Africa with their treatment in the US: "New York's like Johannesburg, LA's like Johannesburg, Freedom ain't nothing but a word, Let me see your ID." Then, in the early 1990s, Jesse Jackson, still black America's most recognisable face abroad, offered himself as an alternative ambassador to Iraq even as the Pentagon was preparing for war and returning with freed hostages.

Today, one of the most prominent figures on the American music scene is Sean Combs (Puff Daddy, now P Diddy), proudly declaring, "It's all about the Benjamins" (American inventor and statesman Benjamin Franklin appears on the $100 bill). Combs is not so much a music-maker as a brand: you can wear his Sean John line of clothing, or eat his Seafood Pan Roast with the black bourgeoisie at Justins, the restaurant he founded that is named after his son. His role model, he said recently, is not Martin Luther King but Martha Stewart - the Delia Smith of middle America, whose name sells products at an astonishing rate.

At some point, following the passing of civil rights legislation in the mid-1960s, an economic fracturing within black America gradually produced a rupture in relations between black America and the rest of the diaspora. This was by no means a seamless transition. Soul singer James Brown went on a US-sponsored tour of Vietnam in 1968; a year later, the late James Farmer served in the Nixon administration as assistant-secretary for health, education and welfare. Throughout the 1960s, baseball supremo Jackie Robinson remained a committed Republican and a fervent supporter of America's role in the cold war. But so long as those opportunities remained limited, resistance was widespread. So much so that even those who had either opted for or been co-opted by the white-dominated mainstream have felt compelled either to qualify their allegiance to the right through racial assertion or simply to quit altogether. Shortly after Brown returned from backing the troops in Vietnam, he recorded his anthem "Say it loud - I'm black and I'm proud"; Farmer left the Nixon administration in disgust; Robinson left the San Francisco Republican convention that nominated Barry Goldwater, the party's most rightwing candidate of the past century, saying, "I had a better understanding of how it must have felt to be a Jew in Hitler's Germany."

The growing differences within black America started to be replicated in the huge disparity of experience between black America and the rest of the diaspora. In 1995, black Americans spent $1.2bn on hair care, a little more than the GDP of Gambia, the home of the ancestors of Roots author Alex Haley.

The combination of more wealth and less consciousness undermined the potential for solidarity with other black people from poorer nations. This has been most vividly expressed culturally. Upon arriving in Zaire for The Rumble In The Jungle, Ali declared that he was "home". In contrast, in 1992, when the dons of global basketball, the US Dream Team, went to the Olympics in Barcelona, the US Olympic committee begged Charles Barkley to tone down his comments after he hit an Angolan player. Among other things, Barkley said, "The guy probably hadn't eaten in a few weeks... I'll hit a fat guy next time... I thought he had a spear."

Underpinning all of this has been a profound sense of patriotism that informs US political culture across the boundaries of race and ethnicity. Martin Luther King, we should not forget, insisted that his dream was "rooted in the American dream". This should come as no surprise. Bar a handful of pilgrims and the Native American Indians, African-Americans are the ethnic group with the longest, geographical attachment to the US. Unlike other racial minorities in the west, they are not relatively recent immigrants. So, in times of national crisis, they rally around their flag in a way that those of Arab descent in France, say, or of Caribbean descent in Britain could not imagine. A New York Times poll last year showed that 75% of black Americans approved of the performance of President Bush, while another, by the Pew Research Centre for the People and the Press, showed that 68% backed the war against Afghanistan. The fact that this level is significantly lower than whites - 90% and 88% respectively - shows that race still has a considerable impact on national allegiance. "It's about a contradiction in their own lives," says Keith Woods of the Florida-based Poynter Institute. "About the difference between feeling like Americans and at the same time feeling like America hasn't fully embraced them."

This contradiction has found full expression in a ferocious debate within black America itself. In October, the singer and one-time civil rights activist Harry Belafonte compared Powell to a "house slave". "Colin Powell's permitted to come into the house of the master. When Colin Powell dares to suggest something other than what the master wants to hear, he will be turned back out to pasture." And the online magazine In These Times describes Bush's entourage, the most diverse in US history, as "Uncle Tom's Cabinet", saying, "It is a sad, ironic testimony to the current complexities of racial politics in America that African-Americans like Colin Powell and Condoleeza Rice can attain unprecedented career advances in tandem with the sweeping disenfranchisement of thousands of black voters." The most dominant campaign among black activists on the left, over the past few years, has been for reparations for slavery - a movement that has sought to cement links with the developing world and with Africa in particular.

So the shift from internationalism to insularity within black America has never been straightforward - and, far from being complete, remains very much contested. In common with all Americans, the events of September 11 are forcing Black America to reassess its relationship with the world. But there can be little doubt which way the pendulum is swinging, or of the impression that is being given globally. In the words of a South African columnist shortly after September 11, "Even aggrieved minorities are Americans first. For as much as [they] like to uphold the roots of [their] ancestors and look to Africa as a point of origin, the US is [their] home. At this moment, [they] probably wants those terrorists 'smoked out of their holes' as Bush threatened. That makes [them] as American as [their] president."