Small white coffins on our shoulders

Up from the row of grey subway steps, into the sunlight. I started walking a bit hastily, not quite sure which way to go. I was looking for Brooklyn College, but the area I came upon was a fairly rough-looking one. Small brownstones, shattered stoops, bent ironwork railings, mismatched curtains, radios propping open the windows. Music wafted out and seemed to hang in the air, then drop. Women sat on the steps, with the street-corner stare of those who have seen too much. They looked along a row of dented cars and broken fire hydrants.

I've lost most consciousness of being a white man in New York, but every now and then it returns with force: you become acutely aware of your skin, which in America is often still another form of wallet.

My chest tightened. Slanted shadows cut sharp corners. It felt like curfew. I turned to re-tread my steps, back to the subway station, when, oddly, out of the corner of my eye, I saw a group a group of African-American men in dark suits and ties coming out from a house on the side of the street still in evening sunlight. One held a trumpet. He paused on the top step, then shined the trumpet on the leg of his trousers. Behind him came a few other musicians, then a number of women and children, impeccably dressed in an old-fashioned way. You could almost feel the run of fingers against the starch of their collars. Behind them again came – on the shoulders of just two teenage boys – a very small white coffin. The trumpeter pulled down a note of blue from the sky. The procession twisted its way out onto the street. The cars stopped. The oxygen was gone from the air. It was not a jazz funeral, not in the traditional sense anyway, but there was a magic about it. The trumpet hauled down a darker note from the shadows: sometimes there's nothing harder to deal with than a small coffin.

They bunched together on the pavement, carrying the box down the road to what I presumed was the local funeral home. But I didn't follow and I tried not to stare. It was not my place. That was a year ago, just a couple of weeks after Hurricane Katrina, and it struck me then that the box was so small it might not even have held a child – it could have been something else altogether, a way things once were.

A full year has passed since Katrina and the best part of what George Bush has said is perfectly boiled down by a statement from a recent press conference where he urged tolerance for the rebuilding of the American Gulf. "This was a huge storm," he said. "People have to be patient." Even for an idiot, he can be patently idiotic. His lack of empathy for the people of the Gulf is stunning, even for a spoiled, rich Connecticut-born boy. Today there are thousands of people attempting to return to their barely-damaged homes in New Orleans, but they are being kept out by barbed-wire fences, armed guards, snapping dogs. It's a scene reminiscent of a refugee camp in some ill-starred part of the world.

New Orleans is the place where all of America flows down to the sea – it is the literal catchment of all the rivers on the eastern side of the Rockies. How that city goes is how the rest of the country goes. The rest of the world was shocked by the images of a nation allowing its people to be marrooned by neglect, but really it has been a reflection of a presidency that doesn't give a toss.

If John Steinbeck's Grapes of Wrath held a requiem for a certain type of American west, then Spike Lee's new documentary When the Levees Broke will have most people understanding the need for small white coffins. A four-hour masterpiece – decently polemical and outraged – it has just come out in the States and is as acute a portrait of a country as it is a damning portrait of the powers-that-be.

The aftermath of Katrina – perhaps even more than the war in Iraq – is still tearing its way through the heart of what was once perceived as American innocence. But not even American innocents can feel too good about the moral temperature of this country any more. In the same press conference where Bush wagged his finger (where he took it from, Lord knows) and told people to be patient, he also came up with the spectacular thought adage, when talking about Iraq: "War is not a time of joy."

See him there, turning away from the microphone, carrying all those small white coffins on his shoulders.