THE preamble to the Constitution of the United States begins with a lofty statement using language borrowed from the 1707 Act of Union, the intention to create what it calls “a more perfect Union”.

If those words have an aspirational quality, it was intentional, for Americans often speak of their constitution as a work in progress. And if the recent Republican and Democratic National Conventions are anything to go by, there’s lots of room for improvement.

In her speech accepting the Democratic nomination on Thursday night, Hillary Clinton reflected on events in Philadelphia – “the birthplace of our nation” – 240 years ago, deploying her party’s slogan of stronger together (sound familiar?) to warm that the US was “once again at a moment of reckoning”, with powerful forces “threatening to pull us apart”.

With these words the former First Lady risked echoing Donald Trump’s apocalyptic language at his party's convention the week before, a generally gloomy analysis of a once great nation on the wane economically, democratically and culturally. The system, he had said, was “rigged” against normal American citizens, and only he could fix it.

And in some respects Clinton agreed, up to a point. “I believe that our economy isn’t working the way it should”, she said in her speech, “because our democracy isn’t working the way it should.” This sounded bold, but the proposed solution didn’t quite measure up: the appointment of Supreme Court justices who would “get money out of politics” and, “if necessary”, a constitutional amendment.

This betrayed the narrow scope of constitutional debate in the United States. In both Cleveland and Philadelphia, I met thoughtful Republicans and Democrats who believed their system of government was increasingly ill-equipped to deal with a polarised electorate, a Congress at permanent loggerheads and the increasingly unpredictable nature of Western democracy. Brexit, for example, was very much on lots of minds.

As the outgoing Commander-in-Chief reflected in his tour de force on Wednesday night, “we’re not done perfecting our Union”, but how to perfect something so difficult to alter? Even Clinton’s promise of an amendment to overturn the Supreme Court’s decisions relating to campaign finance seems doomed to failure, for it would require a two thirds majority in both the Senate and House of Representatives, as well as ratification by three quarters of State legislatures.

This has only happened 27 times (the first 10 as the “Bill of Rights”) and even if the Democrats end up controlling Congress following November’s election it appears an impossible threshold. There’s also a cultural problem, for many regard constitutional tinkering as off limits; the Republican “platform” (manifesto in UK parlance), for example, talks of the US Constitution “not as a flexible document” but an “enduring covenant” that must be “preserved uncompromised for future generations”.

A lot, of course, rests with the US Supreme Court, and the fact – odd to an outsider’s ears – that several vacancies will be filled by the next President features prominently in campaign rhetoric. Donald Trump promised to appoint justices who would “uphold our laws and our Constitution”, replacing the late Justice Scalia with “a person of similar views and principles”, a reminder that the supposedly sacred separation of powers is more theoretical than real (the recent UK Supreme Court ruling on the Scottish Government’s named persons policy provides an interesting contrast – no serious politician viewed it as politically driven).

Hillary Clinton, meanwhile, viewed the Constitution in more liberal terms, promising judges who would “defend the constitutional principles of liberty and equality for all”, although she also made a point of contradicting Trump’s claim that she intended to “essentially abolish” the Delphic amendment concerning “the right of the people to keep and bear Arms”. “I’m not here to repeal the 2nd Amendment,” she said. “I’m not here to take away your guns.”

It was another acknowledgement of how powerless the leader of the free world can find his or herself in a domestic context. The US Constitution takes pride in what it calls “checks and balances”, but too often these check and balance proactive reform almost to destruction (just look at Obamacare). And even were Clinton able to overturn liberalised campaign finance and maintain a liberal majority in the Supreme Court, would that really amount to a fundamental rejuvenation of American democracy?

Of course it wouldn’t, for if US politics is increasingly and debilitatingly polarised – and almost everyone agrees it is – then it’s because the electoral and political system makes it so. Just imagine a permanent independence (or European) referendum lasting two years – every four years – and almost constant campaigning. And, at the end of it all, the 55 per cent of Americans who bother to vote are compelled to choose between two candidates many find equally uninspiring.

Third parties or candidates, meanwhile, come and go. When I was a teenager visiting the US with my family during the 1992 election we encountered lots of people planning to back the “Independent” presidential candidate Ross Perot, who went on to manage an impressive 19 per cent of the vote. This time it seems lots of unreconstructed Bernie Sanders supporters intend to support the Green candidate Jill Stein, but even if she (or the Libertarian candidate Gary Johnson) get into double figures, they’ll garner no Electoral College votes and thus make little impact.

Talking of the Electoral College, debates about reforming that – along with other aspects of the US Constitution – have a Groundhog Day quality: every four years pundits and politicians raise the prospect of change and every four years nothing in particular happens, for the system requires a clear winner and that winner, as already discussed, usually isn’t in a strong position to deliver that change.

And it isn’t just the presidency, it’s everyone else too. I heard lots of grumbling over the past two weeks about all of the above, but beyond waving placards in Cleveland or Philadelphia no one had a plan. You have to go all the way back to Woodrow Wilson to find a serious attempt at holistic reform of the US Constitution; he believed the separation of powers orthodoxy was inefficient because it meant the various branches of government were busy attacking and struggling against one another rather than solving contemporary problems in a co-ordinated way.

Today that would be characterised as “gridlock” in Washington, but Wilson was essentially correct: a codified constitution might be necessary but it is by no means sufficient, particularly not when the “big tent” electoral strategies associated with Reagan and (Bill) Clinton have so clearly broken down.

All Woodrow Wilson’s various proposals for a Cabinet or Parliamentary form of government in the United States, of course, failed. With 100 days to go, might the election of Donald Trump – whose familiarity with his country’s Constitution appears fleeting – provoke some fundamental rethink? A lot of Republicans and Democrats, albeit for very different reasons, appear to think so.