If you find yourself afflicted by a sudden urge to destroy the BBC, I have the ideal remedy: spend some time in the United States. A few hours flicking between Fox News and MSNBC should soon see you right. The more time you give it, the more effective it’ll be – and not necessarily for the reasons you’d expect.

The need arises because the BBC is under threat – yet again. That’s hardly a surprise, since this country is now ruled by a Conservative government with a hefty majority, and the Tories have had the BBC in their sights for the best part of 40 years. But the peril has come quickly.

People grumble about the NHS and BBC but one merely has to pose the alternative to see how strong the attachment remains

Tony Hall has resigned unexpectedly early as director general. Next week the BBC will announce major cuts – around £80m – to its news operation, of which the axing of the much-admired Victoria Derbyshire show is a mere foretaste. And this week the Guardian unearthed a 2004 call by a thinktank run by Dominic Cummings, now the prime minister’s most senior adviser, for the “end of the BBC in its current form”, branding the broadcaster the Tories’ “mortal enemy”.

In that spirit, Cummings’s boss has already imposed a ban on his ministers appearing on Radio 4’s Today programme and offered, as one of his rare departures from the words “Get Brexit done” during the election campaign, the suggestion that the BBC licence fee has had its day. Given that a review of the BBC charter gets under way in 2022, none of this bodes well.

It means defenders of the BBC will have to plunge once more into the familiar battle. (I put myself in that category and not only because – full disclosure – I present The Long View series for Radio 4.) The country needs and cherishes those few spaces, like common land, which are governed by something other than profit. It’s not a coincidence that two of the institutions that not only inspire public affection but are seen to define British identity are bodies created in the last century, and are equally available to the millionaire and the pauper – the NHS and the BBC.

People groan and grumble about both, as they always have, but one merely has to pose the alternative to see how strong the attachment remains. Just as voters recoil from the notion of a privatised healthcare system, in which the sick would have to present their credit card to a (possibly US-owned) company, so they would surely balk at a media landscape shorn of the BBC and dominated by the tech giants, in which Britons watch and listen to material overwhelmingly provided by the likes of Amazon, Netflix, Apple, Facebook and Google.

Play Video 1:25 Johnson says he is 'looking at' scrapping BBC licence fee – video

Freed of commercial pressure, thanks to the licence fee, the BBC has the weight to do big, expensive stuff (the Olympics, Attenborough, Strictly, a royal wedding or funeral); to provide financially thankless but socially necessary services (local radio, the Scottish Gaelic-language network); and to take a chance on something that might not have worked but did (Fleabag). Even if there will be individuals who never watch or listen to any of it – and two in three Britons listen to BBC radio every week – the country’s collective life would be undeniably impoverished without it.

Those on the right – who insist Brexit frees us to become Global Britain, punching above our weight – should think especially hard before taking an axe to the BBC. The broadcaster is one of a small group of British assets with a world-class reputation; it counts as part of the country’s soft power, a resource that may be both depleted and more necessary after next week’s exit from the European Union. The consistent Brexiter would be looking to expand the BBC’s muscle, not drain away its lifeblood.

But there’s a further argument for the BBC, newer than the rest but perhaps more vital. Which is where a stint in front of America’s cable TV news channels would prove so useful. For what quickly becomes clear is that in today’s US, there are Fox News facts and MSNBC facts; red-state facts and blue-state facts; facts from the right and facts from the left. All often with little overlap between them. A partisan epistemology rules, so that what you believe depends on what group you belong to. The result is a cacophony, two opposing teams shouting at each other, with no way of sorting truth from falsehood.

The ongoing impeachment trial of Donald Trump is a case in point. Fox viewers, who account for a big part of his base, are kept in the dark about the essential facts of that case because the network simply withholds information that would reflect badly on the president. Indeed, a 2015 study by a former Reagan and Bush official found that those who watched Fox News were less informed about current affairs than those who watched no news at all.

Of course, a contest will always rage between opinions from the right and from the left, but in the past those opinions would proceed from a shared basis in fact. No longer. Combine that with Facebook’s explicit policy of running political ads even when their central claims have been proven false, and you end up with a society in which there is no agreed body of facts. Without that, democratic decision-making becomes impossible.

We have seen that danger in Britain, not least in a Brexit referendum campaign in which contempt for the facts was a central feature, but we have not sunk as deep. Part of the explanation lies with the BBC. For all its flaws, it still serves to hold the ring, to demarcate a clearing in the forest of claim and counter-claim, where certain facts can be established. Once the BBC declares something to be a matter of fact, rather than partisan dispute, that itself becomes a fact, around which politicians and public figures have to negotiate.

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You could see that in the MMR crisis, in which the BBC eventually made clear the scientific consensus had declared vaccines safe. Or its stance on the climate emergency, now the broadcaster has decided it need not pretend this is an issue to be debated between two equally respectable sides.

To be sure, the BBC took too long to get there, falling into the trap of both sides-ism, just as it gets other things wrong. One former BBC News executive witheringly describes a BBC worldview that is remainer-ish on Europe and status quo-ish on domestic policy, which “meant it never got Brexit in 2016 or Boris in 2019”. Things are likely to get worse with next week’s cuts, which will further reduce BBC News, says that ex-bigwig, while investment “goes into questionable extensions of the BBC brand”. Meanwhile, trust in BBC journalism is falling.

And yet trust remains higher for the BBC than it does for the rest of journalism, including the upmarket papers. It aspires for a neutrality and impartiality that, even when it falls short, stands as a bulwark against the steady slide towards post-truth. Sky News and ITV News share in that, which is to Britain’s benefit. But it’s the BBC that established the norm, setting the pursuit of factual objectivity as the broadcasting standard.

The BBC can be maddening, prompting both left and right to tear their hair out. But in a world of fake news, we need a broadcaster free of commercial pressure, one that aims to stand aside from the partisan din. It may not always get there. But without it, our grip on the truth would get even looser.

• Jonathan Freedland is a Guardian columnist