I first visited the United States as a teenager in 1970, when the number of people living here who had been born abroad was 9.6 million. Just a decade later, it had risen to 14.1 million. By 1990 the figure was 19.1 million, and in 2000 there were 31.1 million people living in the US who had not actually been born here. Overall, according to the Centre for Immigration Studies, 7.9 million people have moved to the US in the past five years - two and a half times the total that came in the last record wave of European immigration, a century ago.
But if you think this means America is still a land that welcomes the tired, poor and huddled masses yearning to breathe free - to quote those wonderfully idealistic words by Emma Lazarus, written in 1883 and still proudly exhibited on the Statue of Liberty as if they were true - think again. Isn't this, after all, a nation of immigrants that constantly strengthens itself with new blood and brains? The likes of Bill Gates and Microsoft certainly want it to be: not long ago he made a rare visit to Washington to lobby for more visas to be granted to people from countries such as India, because he knows from personal experience that well-educated youngsters from these backgrounds have the know-how and eagerness that native-born Americans simply do not possess.
Nor is there any good reason why America cannot take a limitless number of such immigrants for the foreseeable future: it is a land so huge that there are still only 30 people on average living in each square kilometre, compared with 243 for (say) Britain. European immigrants were welcomed with food, medicine, beds, showers and documentation on Ellis Island a century ago; but any day now my friend Bill Frist, Republican leader of the Senate and a presidential contender for 2008, will introduce a bill to order fleets of helicopters and surveillance aircraft, the construction of giant concrete walls, and $2bn-worth of "border-patrol agents" to keep immigrants out of the land of the free.
Frist is basically a decent fellow, too. Yet there is an ugly mood of racism sweeping this country in which the casually brutal word "illegal" is used as a noun, even by the most enlightened, to describe fellow human beings who live and work here but do not have the documentation to do so legally (though that in itself is only a felony, rather than a crime). Every weekday evening at six o'clock on CNN, there is a "news" programme, fronted by a foaming, red-faced fellow called Lou Dobbs, and dominated by racist, anti-immigrant diatribes that are positively fascistic (and I do not use the word lightly). In such a climate, the "Minutemen" - the white, self-appointed "vigilantes" who venture into border deserts at night armed with shotguns to hunt down illegals - are the patriotic heroes of our times.
The difference between this anger of 2006 and the complacently white-dominated America of Walter Cronkite and Lucille Ball to which I came as a teenager is simple: in 1970, 63 per cent of the immigrants to the US had been born in Europe or Canada, but today the newcomers are mostly Latino. To put it simply, most Americans do not want brown wogs - and especially not when, relying on figures from reputable bodies such as the Pew Hispanic Centre, between 11 million and 12 million of them can be contemptuously dismissed as illegals. I repeatedly come across white Americans dismayed that their country has so rapidly become one-seventh Hispanic. Nothing enrages them more than when they hear the computerised voice that answers the phone, "For English, press 1 . . . for Spanish, press 2," followed by the same announcement in Spanish.
All this puts Bill Frist, George W Bush et al in a quandary, however. They know that most white Republican voters, work-ed into a frenzy by the likes of Lou, want a bill that is much more swingeing than the one Frist is proposing, but they also realise that - to paraphrase Fernand Braudel - capitalism knows no boundaries, and that American business craves not only legal computer whizzes from India but also illegal cheap labour.
Illegal workers, after all, are needed to do jobs that Americans spurn: house-cleaning, fruit-picking and looking after rich white brats. To take just one specific example: the American Farm Bureau, perhaps the lead lobbying group for US agriculture, says that the US would lose between $5bn and $9bn a year in fruit, vegetable and flower production if "guest workers" (the language becomes quaintly benign when the speaker seeks a different emphasis) were not able to sweat in the fields for a pittance.
This, the imperative of Braudellian economics, is problem one for the Republicans. Problem two is purely political: even though a significant proportion of these newcomers do not have the vote because they are illegals, the Hispanic vote is of crucial importance to all politicians, Republican or Democrat. No candidate making a speech in recent presidential campaigns has failed to throw in a few words of Spanish at the first chance, so he can appear on the Spanish-language TV stations that evening. "¡Sí, se puede!" ("Yes, we can!") thundered the triumphant chant of Hispanics as they marched through DC on 10 April. "The sleeping Latino giant is finally awake," said Jaime Contreras, president of the National Capital Immigrant Coalition.
Previous big-time Republicans underestimated the sleeping giant to their cost. A former senator named Pete Wilson ran his 1994 campaign for the governorship of California on a platform of denying benefits, education and healthcare to illegals ("they just keep coming"). He proceeded to win the seat by a landslide and was even thought, briefly, to be a contender for the presidency. But then Hispanic political groups got their act together, his governorship fell into disarray and he was run out of office, never to be heard from again (certainly not by me).
I find terrible ironies about the wave of racism being directed towards America's Latinos, 78 per cent of whom are Mexican. For example, in all the millions of words written or spoken on the subject in the US media in recent weeks, I have not come across a single reference to the fact that large chunks of the US where their presence is seen as so problematic - Texas, New Mexico, California itself - were part of Mexico until they were forcibly seized by the US in 1846-48, in what is still proudly referred to in the school textbooks here as American "expansionism", carried out in the name of the nation's self-proclaimed Manifest Destiny. The rest of Mexico was invaded by the US army then, too, and escaped the same fate only when congressmen realised that the result of seizing the entire territory would be millions of brown US citizens - something said openly then, but only covertly now.
Nor have I ever seen one single textbook that mentions how Mexican Americans - including legal residents and even US citizens - were kicked out and sent to Mexico during the Great Depression. It's true, though, American readers: check it out. The final irony is that the Latino newcomers are a remark- ably peaceful, hard-working and gentle lot: one academic study found that Hispanic immigrants are 45 per cent less likely to commit violence than third-generation Americans.
Nevertheless, polls by both Time and the Pew Research Centre find that Americans believe - by majorities of 68 and 74 per cent, respectively - that (in the words of one question in the Pew poll) "immigrants today are a burden on our country because they take our jobs, housing and healthcare". There are some respected academics, such as Professor George Borjas of Harvard, who argue that the arrival of immigrants has lowered the incomes of established Americans by as much as 5 per cent; the general consensus, however, is that their presence has had the effect of raising it very slightly, perhaps by less than 1 per cent.
What is indubitable is that the lives of many white Americans would fall apart without the work of Latinos. I know of one lady in San Dimas in California, for example, who was aghast when her gardener (an illegal immigrant, naturally) told her the climate of fear was such that he could no longer risk driving to work without a driving licence. So she did what any self-respecting wealthy white woman in California would do: she promptly hired him a chauffeur of his own. Without Hispanics, after all, who would trim our hedges, cut our grass and unblock our sewage pipes?