They say that today is going to be the greatest party in the history of the United States – a collective explosion of Bud-fuelled Springsteen-soundtracked patriotic fervour.

So, I hope it is not too much to ask, amid all the rejoicing, that the people of America remember whose project this all was in the first place.

As the cheerleaders cartwheel down Main Street in their stars and stripes bikini bottoms, and as the gases of a billion broiled hamburgers ascend to the skies, I hope someone will look at the names of the people who actually signed that Declaration Of Independence 250 years ago today – and see what they have in common.

They are all Brits, all 56 of them. They are all the sons or grandsons of British settlers. The whole thing is not the result of some autochthonous* American political revolt but the logical consequence of the 18th century English enlightenment – from John Locke to Edmund Burke.

Until the final rupture with the hated over-taxing government of George III, men like Thomas Jefferson and Benjamin Franklin saw themselves as British – loyal servants of the Crown – and they believed that in launching their rebellion they were sticking up for ancient principles forged in England: the rule of law, representative government, trial by jury and no taxation without representation.

I mention all this because we Brits should take parental pride in the very existence of modern America – perhaps the most extraordinary of all Britain’s contributions to the world today.

I also mention it because the specifically British ideals on which America was founded are responsible for that country’s current astonishing success and will ensure that America remains the dominant world power for a century to come, or more.

You doubt me? Look at the facts. Compare the US and China, and the long-term prospects of those two great countries.

For about 20 years it has been conventional to say that China is soon going to displace America as the world’s hegemonic power.

The logic at one stage seemed inescapable.

China’s 1.4 billion people have been embarked on a breakneck and highly successful programme of industrialisation, and by a judicious mixture of authoritarianism and capitalism (and currency manipulation), China has become the world’s biggest exporter, with a big lead in green technology such as solar panels and electric cars. China is now the world’s second largest economy, with a rapidly expanding military.

Since the American population, at 342million, is only a fraction of the size of China’s, foreign policy analysts have long since talked about the moment when China becomes top dog, sometime in the next few decades.

They have warned about something they call the Thucydides Trap, after the great Athenian historian and general. This is the risk that in the struggle for primacy, the two superpowers will inevitably come into conflict.

As Thucydides puts it in his account of the Peloponnesian war: ‘It was the rise of Athens, and the fear this inspired in Sparta, that made war inevitable.’

China’s President Xi Jinping has been quoting the ancient Greek historian for years, and when Donald Trump recently went to Beijing, Xi asked him, rather grandly: ‘How can we avoid the Thucydides Trap?’

By which he meant, how can we avoid coming to blows, given that my country is inevitably going to overtake your own.

To which the answer is that the whole thing is utter rubbish. There is no risk of a so-called Thucydides Trap, because as time goes on it becomes ever clearer that in most key respects the American lead is pretty much unassailable.

China’s rise to pre-eminence will take far longer than people used to imagine and I frankly doubt that it will happen at all.

Take hard power first. The US spends about a trillion dollars a year on defence, more than three times the Chinese budget, and as a result is the only country that can express its power freely around the world. The Americans have 11 nuclear-powered super carriers, while the Chinese have only three, none of which is nuclear.

The Americans have 50 nuclear-powered attack submarines; the Chinese have about eight. The US has a vast lead in aviation, especially long-range bombers, in space and most other key technology. And perhaps even more importantly, the US has experience of actual warfare.

For better or worse US armed forces have been engaged in almost continuous effort overseas since the Second World War, from Korea in the 1950s to Iran today, whereas China’s last experience of fighting was, arguably, in Vietnam in 1979.

The Americans have hundreds of bases – some of them colossal – in dozens of countries around the world. They have important alliances with such countries as South Korea, Australia, the Philippines and Japan, as well as the 32 Nato countries – plus they have 5,000 nuclear warheads. China has one overseas base, in Djibouti, and a few hundred nuclear warheads, and no military allies to speak of.

If you ask how on earth America can support these commitments, the answer is that it has a massive and dynamic economy. Think of all the publicly quoted companies in the world – all the companies in which you can buy shares. American companies currently make up 65 per cent of the total stock market value of the world.

No currency has come close – in spite of repeated efforts – to replacing the dollar as the world’s reserve currency; not the Yuan, not the Euro, not gold. Today 58 per cent of the world’s foreign exchange reserve is held in dollars, while oil and other commodities are still priced in dollars, and there is no sign that will change.

Neither China nor any other country have companies as huge or as innovative as the US tech giants and the average American is still much, much richer than the average Chinese – with US per capita GDP at $94,000 per year, as against under $15,000 per year in China. In trying to predict the future, we should obviously try to understand the reasons for America’s current economic robustness.

It is partly to do with geographic luck and natural resources. America is a beautiful and relatively under-populated continental economy, bounded and protected by two oceans, with friendly neighbours to the north and south.

The US has enormous quantities of arable land, navigable rivers and more hydrocarbons than anywhere else on earth. The Chinese produce a lot of solar panels and have made a great success of their low-carbon industries but that is partly because they have far less oil and gas.

The US is currently producing between 13.7 and 13.9 million barrels of oil a day – which is about 40 per cent more than Saudi Arabia.

The US produces about a quarter of the world’s natural gas but is also taking big bets – despite what the Trump administration says – on renewables such as solar and wind.

Most of the money going into nuclear fusion is now American and if that technology ever comes off it will be American capitalists who reap the rewards.

America’s natural reserves of energy are prodigious and – more importantly – so is the energy of its people.

It has the most extraordinary and ambitious mixture of human capital. There is a reason why the US has moved into complete dominance of the world’s most important new technology – Artificial Intelligence – namely that virtually every

state has a great university and a tech eco-system, with start-ups and spin-offs that are capable of becoming the next Anthropic or Nvidia.

These companies can find the finance in America’s vast capital markets and they can find the original minds in its labs and libraries. Of the top 100 universities in the world typically 30 to 40 are in the US and they maintain and extend their lead because they attract the best from around the world.

There are currently about half a million foreign postgraduate students in America; and there is a very simple reason for that – namely that the US remains very largely open to talent. Whatever the anti-migration rhetoric, America is still substantially an immigrant society, with 28 per cent of the current population either immigrants or the children of immigrants.

In New York, the most populous and productive city in America, 38 per cent of the population was born abroad (almost exactly the same proportion as in London, the most populous and productive city in Britain).

It is a very different story in China, where around 0.1 per cent of the population was born abroad and where immigration has been traditionally very low.

Now that the Chinese birth rate has plunged to half what is needed to maintain a stable population – about one baby, or fewer, per woman of child-bearing age – we are seeing the unexpected collapse of China’s demographic advantage.

On current trends, and without immigration, the Chinese population is expected to shrink to 632 million by the end of the century, while the American population will rise to 421million.

If these figures are anywhere near correct, we are going to see a big narrowing of the population gap – and long before the wealth gap has closed.

The idea of China’s inevitable rise to global supremacy was based on demographic assumptions that are turning out to be wildly off the mark.

It looks very likely that the Chinese are getting older much faster than they are getting richer – while the Americans, with about a quarter of the population density per square mile – have room to breathe and grow.

Of course, things could change. The Chinese could recover their reproductive zap, or they could welcome huge numbers of immigrants – but both seem unlikely.

The crucial difference is that people want to make their lives in America, and see opportunity in America, in a way that applies to very few other countries in the world. They already know American music and American films, and can start to feel at home there – and start to feel American.

The reason they want to go to America is because whatever the flaws of American society – the high school shootings, the homelessness, the opioids – and whatever the embarrassments and polarisation of American politics, people going to the USA know that they will enjoy some extraordinary benefits.

You will have your liberties protected by the Constitution. You will have the right to say what you think and to live your life as you please provided you do no harm to others.

Above all, you will have the right to exercise control over your own government – to elect and kick out those who make the laws.

And who wrote that democratic constitution?

Who gave the American people those rights and freedoms that are to this day the guarantee of their phenomenal prosperity?

It was a bunch of British colonials who, in 1776, were rightly exasperated beyond endurance by the bone-headed stupidity of the British prime minister Lord North and his administration.

Those ideals are ensuring America’s success today and will continue to make America the leading country on earth – well into the lifetimes, I predict, of my great-great-grandchildren.

So happy 250th birthday to the USA – from an original idea by Britain!