While British voters can look forward only to the squirming of a lame-duck Prime Minister and a discredited House of Commons, America is starting one of the most important policy debates in its modern history. Barack Obama describes his promise to create a system of healthcare that would guarantee to all Americans the basic medical treatment taken for granted in other advanced democracies around the world as the defining issue of his presidency.

President Obama's attempt to reform healthcare could set the US's political direction for a decade and will certainly be a more decisive influence on its economic future and the long-term solvency of the US Government, than the recent arguments about bank bailouts, toxic assets and federal deficits.

Europeans are usually shocked that 47 million citizens of the world's richest country have no health insurance and so could, at least in theory, die because they cannot afford medical care. Whether America's traditional insistence that citizens should take responsibility for their own healthcare is proud self-reliance or shameful inhumanity is a matter of political perspective. But increasing ideological polarisation has prevented a consensus forming on whether medicine should be viewed as a “public service” or be treated simply as a form of private consumption no different from food, clothes or housing.

But such theoretical and moral issues are no longer the driving force behind US healthcare reform. Whether or not voters have undergone a moral conversion, America has suddenly become aware that its present healthcare system is unaffordable. As Mr Obama pointed out to the American Medical Association, the doctors' trade union largely responsible for thwarting President Clinton's health reforms, carrying on with the status quo is no longer an option. The mind-boggling cost of healthcare, not bank bailouts or property foreclosures, threatens the US Government with bankruptcy and the whole economy with stagnation.

US healthcare costs have long been out of line with costs in other countries. The US spends $2.5 trillion or $8,100 per head on healthcare, 17.6per cent of its GDP. This is half as much again as the 11 per cent of GDP spent in France and Germany and almost double the 9 per cent in Britain and the OECD as a whole. The world's next highest spender is Switzerland at 12 per cent. Yet medical outcomes, such as cancer and cardiac survival rates, are generally no better than the OECD average and substantially worse than in France, Switzerland and Japan.

Until recently, however, these vast disparities made no impression on US public opinion. Americans simply assumed that the rest of the world was out of step: their system might cost more, but it delivered more innovation and greater patient satisfaction than “socialised” medicine.

In a mirror image of the false dichotomies distorting the healthcare debate in Britain, where US-style privatisation is presented as the only alternative to a state-run NHS, Americans have generally reacted to all reform proposals with horror, pointing to the inadequacies of the British system, while ignoring the experience of other countries. France, Germany, Switzerland, Canada, Australia and Japan, for instance, combine public and private provision in ways that deliver far better medical outcomes and greater customer satisfaction than the British system, at far lower cost than the US.

So what is different this time? Last year's financial crisis has focused attention on economic priorities as never before. Politicians and international investors suddenly realise that America's long-term solvency is threatened not so much by the $1.8 trillion temporary deficit created by the credit crunch, but by the looming insolvency of Medicare and Medicaid, the publicly funded parts of the US healthcare system. They cover only 30 per cent of Americans, yet are as costly as Britain's entire NHS and will suffer deficits of trillions of dollars in the next decade if present trends persist.

In the US business community and on Wall Street, the idea of increasing government involvement in healthcare is gaining widespread support for the first time. The obvious reason is the collapse of General Motors and Chrysler, both forced into bankruptcy largely by the ruinous costs of health insurance that they had contractually guaranteed to employees. The fate of the automobile companies, effectively handed over to their unions in lieu of future health insurance, has been a cautionary tale. All large US employers have realised that offering workers private health insurance puts them at a big cost disadvantage against international competitors whose workers are covered by government-financed plans - and in extreme cases, such as automobiles, this exposure puts the survival of entire industries at risk.

Most importantly, individual Americans, whose borrowing power has vanished in the credit crunch, realise that extravagant medical costs are a luxury they can no longer afford. White House officials note that average wages have increased by only 3 per cent since 2000, but health insurance premiums have rocketed by 58 per cent. The long-term erosion of US living standards by health costs is strikingly illustrated in the chart, which shows that America's “excessive” consumption, widely seen as the most fundamental cause of world economic instability, has been due entirely to health spending.

By marshalling evidence such as this, President Obama should be able to convince Americans that their present healthcare system is unsustainable and threatens individuals, the nation and the Government with bankruptcy.

But can he come up with a better alternative? This will mean overcoming powerful lobbies - doctors, medical companies and hospital businesses that profit from medical extravagance; trial lawyers who sue them; unions that use healthcare trusts as a recruiting tool and an instrument of corporate power and, finally, the health insurers that manage the whole sorry mess.

If Mr Obama can overcome this unholy alliance of vested interest on the Right and Left, his place in history will be assured. If not, the crisis from which the US economy is now emerging, will be just a mild portent of things to come.

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