Felix Frankfurter was never a chief justice, as we described him in the article below. He did, however, serve for many years as an associate justice of the US supreme court.

'Whisper of how I'm yearning", sang George M Cohan in one of the great American songs of nostalgia, "to mingle with the old time throng". Well, I'm yearning too, not for the gang at 42nd Street exactly, but for the America that Cohan was indirectly hymning - for the Idea of America, with a capital I, which once made the United States not just the most potent of all the nations but genuinely the most liked.

Perhaps, with a future new president already champing at the bit, we are about to witness its rebirth. As a foreigner I am immune to the rivalries or seductions of American party politics, but I have loved the old place for 60 years, and I simply pray for an American leader to give us back its baraka, as the Arabs say - nothing to do with religion or economics or power or even ideology, but the gift of being at once blessed and blessing.

Of course nobody can claim that the old dreams of America were ever perfectly fulfilled. They often let us down. They were betrayed by the national reputations for crime, corruption, racism and rampant materialism. Not all the presidents, God knows, were icons of virtue or even of glamour, and the benevolent Uncle Sam of the old cartoonists was more often interpreted, around the world, as a fat moron in horn-rimmed spectacles, chewing a cigar. Nobody's perfect, still less any republic.

But I think it is true that only in our time has the American Idea lost its baraka. A generation or two ago, most of us, wherever we lived, loved the generous self-satisfaction of it, if not in the general, at least in the particular. The GI was not then a sort of goggled monster in padded armour, but a cheerful fellow chatting up the girls and distributing candy not as a matter of policy, but out of plain goodwill - everyone's friendly guy next door. To millions of radio listeners around the world, the Voice of America was a voice of decency, and one could watch the lachrymose patriotic rituals of America - the hand on heart, the misty-eyed salute to the flag - with more affection than irony.

For myself, I responded to them all too sentimentally. Like Walt Whitman before me, I heard America sing! I relished the hackneyed old lyrics - Mine eyes have seen the glory, Thy word our law, Thy paths our chosen way, Oe'r the land of the free and the home of the brave, God bless America, land that I love ... Most of the words were flaccid, many of the tunes were vulgar, but as I heard them I saw always in my mind's eye, as Whitman did, all the glorious space, grandeur and opportunity that was America, Manhattan to LA. Sea, in fact, to shining sea.

In those days we did not think of American evangelists as prophets of political extremism - they seemed more akin to the homely convictions of plantation or village chapel than to the machinations of neocons. We bridled rather at the American assumption that the US of A had been the only true victor of the second world war, but most of us did not very deeply resent the happy swagger of the legend and danced gratefully enough to the American rhythms of the time. We thought it all seemed essentially innocent.

Innocent! Dear God! Half a century, and nobody thinks that now. Far from being the most beloved country on earth, today the US is the most thoroughly detested. The rot really started to set in, in my view, with Abraham Lincoln, one of the most admirable men who ever lived. He it was who saw in American glory the duty of a mission. America, he declared, was the last best hope of earth. The pursuit of happiness was not its national vocation, but the example of democracy. The more like the United States the world became, the better the world would be. No statesman was ever more sincere or kindly in his beliefs, but poor old Abe would be horrified to see how his interpretation of destiny has gone sour.

For the missionary instinct, which impelled Americans into so many noble policies, was to be perverted by power. Pace Lincoln, America was not necessarily the last best hope of mankind, and the knowledge that it has possessed unchallengable powers of interference has distorted its attitude to the world and cruelly damaged its image in return.

Isolationism was not a very estimable stance, but interfereism is not much more attractive. In humanity's eye, the swagger has become bombast and the cocky GI has become a bully.

But there is a difference between image and idea. One is a projection, the other an absolute. Public relations people, tabloid newspapers, spin doctors and entertainers can all fiddle with the image of America, but the idea of it remains constant - overlaid, perhaps, dormant, even forgotten, but always there. Everyone who visits America feels it - every package tourist returns to tell their neighbours how nice the Americans are, how different from their reputation. And what they are all sensing, half-hidden behind the image of America, is the presence of the Idea, with a capital I.

When I first went to the United States in the 1950s, I impertinently remarked to an archetypal guru, Chief Justice Felix Frankfurter, that what with Senator McCarthy and southern segregation, and civic corruption everywhere, I was not much impressed by the condition of America. Be patient, said the sage. America is like a pendulum, swinging from good to bad, from bad to good, and before long it will swing again.

He was right, and with luck, perhaps the pendulum is almost ready to swing back once more. Whatever we may think in our moments of despair, America is still a marvellous and lovable country whose patriotism can still be touching: try restraining a tear when you listen to Irving Berlin's setting of the words on the Statue of Liberty - the ultimate American text, with music by the emblematic American immigrant. The Great Republic is great still, full still of decent clever people trying to be good. Even now, it is as free as can be expected, and its democracy is fundamentally honest and robust. It laughs at itself, criticises itself and dislikes itself just as much as we do.

All it needs is someone with a key to unlock that Idea again, and I hope it will be that next president, whoever it is, even now gearing up for the election. Please God, may it be a poetic president. Inspiration has been the true engine of American success, and all its greatest presidents have been people with a divine spark. The dullards may have been efficient, respected or influential, but the Jeffersons and the Roosevelts, the Lincolns and the Kennedys have all been, in their different ways, artists.

So may it be a president with the key of original inspiration who can release the Idea from its occlusion. All the ingredients are still there, after all - the kindness, the imagination, the merriment, the will, the talent, the energy, the goddam orneriness, the plain goodness - all there waiting to burst out once more and bring us back our America, blessed and blessing too.

"Give our regards to old Broadway", sang Cohan, "And say that I'll be there ere long." So will we, so will we, just as soon as America comes home.

· Jan Morris is a historian, travel writer and former Guardian correspondent. Her first book was Coast to Coast: A Journey Across 1950s America and the most recent Trieste and the Meaning of Nowhere