To bowdlerise a remark of Kingsley Amis's, I know I like guns, I just don't know why I like them so much. I enjoy handling firearms, shooting them, too, when I'm offered the chance. The gun safe in my house is empty, however, since, with the possible exception of grey squirrels and burglars, there is not really very much to shoot if you live in London. But the logic of mass ownership of guns seems simple enough: if people carry guns, then people will get shot.

Michael Moore, the American documentary-maker, is much more enthusiastic about firearms than I am. He has been a member of the National Rifle Association since he was 16. He was a high school marksman. Overweight, mild-mannered and habitually dressed like a slob in sweatshirt, jeans and baseball cap, he even has the look of some disaffected nutcase who has just used a semi-automatic rifle to make a name for himself in his local McDonald's. Lately, however, Moore had begun to feel dissatisfied with America's gun laws and, by extension, the American national psyche. And when he and his wife were driving across the country to New York after 11 September, the question he kept hearing from ordinary Americans was: "Why do they hate us?"

Moore thought this was a good question and, having identified American foreign policy as the most probable answer, he uses this documentary to make an excellent case for blaming that same policy on a prevailing domestic culture of fear and paranoia which is mirrored in the way America regards the rest of the world, and on arms manufacturers such as Lockheed Martin which preys on this same paranoia.

Lockheed Martin is the largest employer in Littleton, Colorado, site of the infamous Columbine killings, in which two scrofulous teenagers, armed with mail-order rifles, walked into their high school after an early-morning visit to their local bowling alley and murdered more than a dozen people. Why did they do it, asks Moore.

Having discredited persuasively and hilariously the usual suspects - Marilyn Manson, violent films and "shoot'em-up" computer games - Moore suggests that America's weapons culture is fuelled by fear of the other in society, that other being a young black male. Yet as a public prosecutor tells Moore, the biggest gun problem in America is not, as most people might perhaps believe, with inner-city black gangs but with paranoid, middle-class whites. Talking of whom, Moore doorsteps the veteran actor and NRA chairman, Charlton Heston, who seems to suggest that if it wasn't for all the blacks in America, then no one would need the guns. El Cid just turned a little rancid.

All of which explains, says Moore, how it is that in 2001, 11,000 Americans were killed by guns. In fact, this is a comparatively low figure. The year before, 28,000 Americans were killed by guns; and perhaps the most amazing statistic - which doesn't appear in Moore's film - is the one I used to see on posters in and around LA a couple of years ago, to the effect that since John Lennon was shot in 1980, half a million Americans have been killed by firearms. Is it any wonder that the rest of the world looks askance at Dubbya's "war on terrorism" when there are so many Americans killing each other at home?

America's gun-dependence - like some hopeless crack addict, this is a society that is incapable of giving up its firearms - and apparent indifference to the gun deaths of its own citizens would be bad enough; but Moore goes a stage further and reminds us that American governments of both political hues have made, and continue to make, America the world's largest exporter of weapons of mass destruction, while the CIA has sought, again and again, to replace regimes unfriendly to "democracy" with others more amenable to the global interests of the US. Regimes in countries such as Korea, Guatemala, Vietnam, El Salvador, Cuba, Nicaragua, Chile, Grenada, Afghanistan and now Iraq. And if I do have a criticism of Moore's analysis of America's postwar foreign policy, it is that he makes little mention of how Palestine has been the most egregious example of American military interference abroad. But then this marvellous and funny documentary had to play in New York.

Which was where I saw it; and I was gratified to see the film greeted enthusiastically, even applauded at the finish. Which encourages me to suppose that perhaps this wonderful country will, one day, come to its senses about gun law and, by extension, its Clint Eastwood-style diplomacy. On no account should you miss this film, and, lest it be thought - as some have suggested - that Moore's documentary is un-American, it should also be remembered that Americans enjoy not just the right to bear arms, but the freedom to make films like this.

Bowling for Columbine (15) is released on 15 November