AS the Nobel laureates of the Nuclear Science and Security Board prepared to edge their famous Doomsday Clock closer to midnight last week, there was a distinct sense of time being called on the liberal era. It has become a media trope, a cliché, a cry of pain from the intelligentsia that the lights are going out all over the democratic world.

Certainly, the “long” 20th century, as historians call it, seems to have come to an abrupt end with Britain’s departure from the European Union and Donald Trump’s elevation to the post of leader of what we used to call the free world. The times they are a changing, but not in a good way. America First is now the whole of the law.

For me, one of the more disturbing sideshows to that eerie week was the collapse of the power-sharing executive in Northern Ireland. This had nothing directly to do with Donald Trump, or Theresa May's giving the finger to Brussels in her Lancaster House speech. The proximate cause was a scandal over the mismanagement of a sustainable heating project.

But you got the distinct impression that both sides of the political divide in that troubled province had decided to give up on the rational, co-operative politics that had endured since the Good Friday agreement in 1998. That was brokered by a Labour government, sponsored by President Bill Clinton and financed by the European Union. All gone. It's as if people there are saying: if no-one else is trying, why should we?

Self-interest is back. In America and Britain the mantra is the same: us first. Co-operation, give and take, rules-based international relations are for wusses and wimps. We look after our own. Make America Great Again. Britain for the British. And the Scots can whine and complain all they want – they’ve nowhere else to go, have they?

The audacity of Theresa May's declaration of UK independence last week took many by surprise, but it shouldn't have. She'd made clear in her Conservative Party conference speech that the politics of immigration were now paramount, and that Britain was going to reject the remit of the European Court of Justice. That meant departure from the single currency, though she didn't spell that out at the time.

Theresa May has been transformed into a tabloid reincarnation of Margaret Thatcher in her Iron Lady phase, threatening the European Union with “calamitous self-harm” if they refuse to allow Britain access to the single market on our terms, rather than theirs. We'll draw a veil over the fact that Thatcher was actually one of the architects of the European Single Market, but she certainly had an instinctive suspicion of Europeans – continental ones that is – and a lingering emotional attachment to vestiges of empire. Kith and kin.

England has never felt comfortable with Europe, unlike Scotland, which has historically been more continental in outlook since we started migrating there in the late middle ages. Now, the post-imperial concept of the “Anglosphere” is being dusted down and prepared for use by Iron Lady II. There is an English-speaking world out there, say right-wing historians like Andrew Roberts, to which Britain naturally belongs – including America, Australia, Canada, New Zealand and perhaps even Anglicised India. It is just waiting for the return of British leadership, like Middle Earth in part three of Lord Of The Rings.

But what the neo-imperialists of the Brexit Tory party don’t seem to appreciate is that these countries mostly have stable trading relations already with the European Union that have been negotiated over decades. Canada has just finished one exhaustive free trade deal with the EU that took seven years and nearly collapsed at the last minute over objections from the Belgian region of Wallonia. This idea that somehow the “globe” is waiting for the UK to be released from the malign chains of Brussels is one of the central delusions of Brexit Britain.

There is nothing currently stopping Britain trading with English-speaking countries, or Chinese-speaking ones, for that matter. Germany exports vastly more to America and China than we do, and that is from within the European Union. The point about the single market is that it increases bargaining power with non-European countries. Controlling access to a market of 500 of the wealthiest consumers on the planet means you don't need to make empty threats.

Theresa May's trump card, in her “Global Britain” project, is supposedly the American President of the same name. We'll soon see whether Donald Trump delivers on his promised front-of-the-queue free trade deal with Britain. But it is surely the height of naïveté to believe that the author of The Art Of The Deal is likely to let sentiment get in the way of hard bargaining. This is the most outspokenly protectionist president since Herbert Hoover.

“We well follow two simple rules”, said Trump in his inaugural address, “buy American and hire American.” He won't be messing around with the Transatlantic Trade and Investment Partnership,TTIP – the stalled free trade deal with the European Union that Barack Obama sponsored. It will be renamed something like the Trump Trade and Really Great Investment Deal. And unless Britain signs up as the 51st state of the USA, we're going to be on the receiving end of the 45th President’s central doctrine: America first, last and always.

Donald Trump's speech didn't seek to emulate the soaring rhetoric of Barack Obama. This was heavy-duty prose, not poetry, and he hammered away at the single theme the President has made the centre of his entire campaign: returning to Americans the jobs which he claims have been “stolen” by other countries with the connivance of a corrupt Washington establishment. He all but called Obama and his predecessors crooks. “The politicians prospered, but the jobs left and the factories closed” he roared as five former presidents shuffled their feet behind him. "The establishment protected itself but not the citizens of our country.”

Donald Trump's inaugural address was a breath-taking exercise in narrow-minded economic nationalism. “Protection[ism],” he said, abandoning the economic wisdom of every economist since Adam Smith, “will lead to great prosperity and strength.” He served notice on “all the nations of the world” that American interests will be paramount in every decision he takes. And by the way, folks, they can pay for their own defence because in future America is only concerned with two things: securing American borders and “wiping radical Islamic terrorism [the phrase Obama always avoided] from the face of the earth”.

Notwithstanding Trump's curious bromance with Vladimir Putin, relations with China, Japan, Latin America, the European Union, Nato have already been soured by the President's penchant for the late-night tweet. He only needs to offend India and Africa and he'll have the set. No doubt Scotland will get its turn in the Trump spotlight when he visits the UK later this year.

Scots are left watching this hideous Anglo-American imperial pantomime with mounting anxiety. Do we remain in the UK, or try to seize hold of an EU lifebelt and escape the new Atlantic alliance? Scotland has faced difficult choices in the past in our long history, but never have the rocks looked rockier or the places harder.

But our horrified fascination with the nascent Trump/May axis is surely shared with the rest of the civilised world, which must now contend with the world's only remaining superpower becoming something like a rogue nation, a failed state, an elective dictatorship in which a belligerent and selfish leader is prepared to abandon all the conventions of civilised international relations in the interests of rebuilding the self-confidence of white working-class Americans. God Bless America – they'll need it.