Rupert Cornwell: The richest country on earth has failed lamentably to wipe out its racial and social evils

Around the world, from its pedestal of self-appointed virtue, the United States inveighs against the evil of racial and sectarian divisions. Hurricane Katrina has shown how all the wealth and power of the richest country on earth has not succeeded in removing that blight from its own society.

New Orleans, admittedly, is a very special case. It has long been a byword for civic inefficiency and corruption. Such shortcomings are, however, masked by a beguiling blend of indolence, exoticism and fatalism, whether about potential floods or the material injustices of life. Therein lies the city's myth, and so much of its charm for white outsiders like Bush.

But the truth is different. Yes, blacks may run its politics (after all, African-Americans constitute two-thirds of the city's population, a reality which after the 1965 Civil Rights Act could no longer be denied). But the economic power that matters has always been in white hands. A third of the citizens of New Orleans citizens live below the poverty line, and they are overwhelmingly black.

Unlike on 14 September 2001, when he spoke at Ground Zero, during President Bush's visit to the stricken region on Friday, the son of privilege almost unerringly struck the wrong note. No one, it seemed, had told him about the extent of the devastation. His closest contact with the misery on the ground in New Orleans proper was from a few hundred feet aloft in his presidential helicopter. At one point he even waxed nostalgic about his boozing expeditions to the city of packaged sin, during his frat-boy youth.

But do not blame Bush alone. All presidents are symbols. This one symbolises the ever-growing inequalities of race and wealth in 21st-century America, that no amount of prattle about "compassionate conservatism" can bridge.

Would the authorities have been so inept to respond if a similar calamity had overtaken Boston, Cincinnati or some other prosperous city in the US heartland? Of course not. Would the government have waited five days to mount an all-out relief operation had the colour of the skin of those waiting in some God-forsaken sports arena been white, not black? Of course not.

The United States's habitual solution to the problem of race is to forget it - or to pretend that its black minority is a minority no different from the others that have flocked to the country in search of a better life. But the latter groups came of their own volition. The slaves did not. In America, natural disasters often lay bare this simple truth, and that is why floods, fires and hurricanes are apt to be followed by social and political upheaval.

There is much talk now - and a myriad deeds to prove it - of Americans' generosity and ability to come together in a time of trouble. But in the 10 years I have lived here, I have never seen America as uneasy with itself, as ashamed of itself, as it is now. Just as it has ripped trees from the ground and houses from their foundations, Katrina has torn away many of the country's comforting delusions about itself.

So will the tragedy of New Orleans really bring to its senses the sanctimonious, white-run America that preaches self-help and discipline as a substitute for social spending, and fortified by its sense of virtue, continues cutting taxes for the wealthy and aid for the poor? Don't count on it.

Oh, yes, the Congress will hold hearings into the débâcle when it returns from the summer recess this week - Washington has always excelled at allocating blame. But quickly the political agenda will return to inequality as usual. Next on the agenda of the Republican-controlled legislature will be cuts in Medicaid, the government health-care scheme for the neediest, and the elimination of the estate tax (what we call death duty).

Alas, George Bush is a stubborn man, who can still not even bring himself to admit that the relief effort has been so badly managed. Fortunately, the devastation caused by Katrina has not been shared by all - but the cost of repairing it surely should be. If ever there was a moment for increasing taxes on the better-off, rather than cutting them, and for expanding welfare and other aid for the least privileged in American society, it is now.

But much the same was true of the war in Iraq, a conflict for which 1,900 American soldiers have given their lives, but which has not touched the lives of 95 per cent of the citizenry. Katrina will be little different. The only Americans to make sacrifices are those - overwhelmingly black and poor - who suffered directly from the storm. Thus it has always been, and thus it will remain.