Just as the war broke out I spent a week in Manhattan, contemplating my 50 happy years of association with New York City. I have loved the place always, have made there some of my oldest and truest friendships, and believe it to be an epitome of the essential American dream - the dream, that is, of equal opportunity for every single citizen, in a society peaceable, rich, fair and fun.
I have never considered Manhattan, on the other hand, an epitome of the American city. James Bryce, a century ago, said it was "a European city, but of no particular country", and I have always thought of it more as a gateway, where the idea of America presented itself to the world, while the truth of America was worked out within. Washington DC, Chicago, Los Angeles, San Francisco - these were the places where the nature of the Great Republic had evolved in my time, and for me Manhattan was a kind of beachhead from which one could observe the progress of the continental culture without totally immersing oneself in it - a toe in the waters of Americanness, or perhaps a leg.
Many cities around the world like to think of themselves as distinct from - usually superior to - their parent nations. There are even capitals that are representative of their states only in purely institutional terms. What's organically Australian about Canberra? Where's the Brazil in Brasilia? New Delhi isn't very Indian, and there are times when even Paris stands on a separate plane of Frenchness from the rest of France.
But New Yorkers had seldom thought of their city in quite this way, and as I wandered the streets the other day, working out this piece, I began to think differently myself. It was not simply that the assault on the World Trade Center had made Manhattan symbolical of the nation in a more absolute sense, making it feel less like a city state, more like a rampart. Nor was it that New York was no longer the supreme immigrant city - innumerable others are now just as polyglot and multi-ethnic, just as full of hopeful newcomers. Even the brilliance of the place is far from unique: hundreds of cities across the world can claim to be The City that Never Sleeps, that proud old boast of Manhattan, and modernity itself can seem more modern in many a metropolis of Europe and Asia.
I had long ago come to write about Manhattan in homelier terms, anyway, likening it once to a favourite pair of old boots, and once daringly declaring it, in print, downright old-fashioned. Only now, though, in the spring of 2003, did it occur to me that it was becoming more ordinary, in that it was becoming more like the rest of America. The trauma of the World Trade Center, far from making it even more dramatically itself, seemed to have pushed it metaphorically deeper into its hinterland, and made it rather more like any other all-American city.
This is half in the mind, of course - it is an instinctive, writer's analysis, unsupported by any sociological blarney. But it meant that for the first time in my 50 years of friendship with Manhattan, I felt sorry for the old place.
For hubris is always pathetic, reflecting as it does, by definition, pride before a fall; and it felt to me as though Manhattan, which I had always thought essentially a modest city, for all its majesty, would inevitably be tainted by the hubris that is sadly the prime characteristic of 21st-century America.
Was the United States of George W Bush a proper home, so to speak, for this heart-breakingly beautiful and humane city, so rich in culture and scholarship, and in my experience so profoundly kind? And by extension, I came to think, was Bush's USA a proper ally for us, the British? Years ago I could believe that the so-called special relationship really did represent values held deeply in common, just as whenever I came to New York I felt happily at home in a society that seemed to me essentially good - flawed by crime, corruption and racism, but still representing an influence that was projecting happiness to the world at large.
So far it is still true of Manhattan - this city's example is still benevolent - but think of the harm that the wider American culture has done to us in recent years! From junk food to genetic engineering, from TV trash to unbridled capitalism, from the compensation culture and religious fundamentalism to political correctness gone mad and academic aridity - in a thousand ways, great and petty, the special relationship has tarnished British manners and morals. Even such horrors as indefinite imprisonment without trial (as at Guantanamo Bay) or cruelly administered death penalties (as in Texas) have apparently come to be seen as acceptable behaviour in an ally.
Poor Britain, infected from across the ocean! More to my point, poor Manhattan, separated by only a river from the immense cauldron of shoddiness, false values, deceit, devious ambition and plain crap that simmers at the heart of contemporary America. But there we are. I love the old city still - all the more, perhaps, now that it is tinged in my mind with pathos; and now as ever, when the mist swirls around its skyscrapers, the steam-plumes rise defiant from its streets, old acquaintances greet me with equal kindness from news-stands and posh restaurants. Even now, walking about Manhattan can bring a grateful tear to my eye, if it can no longer set me whistling "Yankee doodle dandy" . . .
Jan Morris's most recent book is Trieste and the Meaning of Nowhere (Faber and Faber, £7.99)