Vladimir Putin must be dreading Monday’s edition of Komsomolskaya Pravda, Russia’s big and breezy tabloid. It will doubtless splash on an explosive interview with Donald Trump ahead of his visit to Moscow, in which the US president will slam Putin’s handling of the war in Syria, suggest US-Russian relations are doomed and lavish praise on the Russian leader’s “very talented” rival. Poor Vladimir must be quaking in his boots.

Oh wait. No interview like that is coming, and not only because Putin would never allow it. Trump himself wouldn’t dare speak so harshly of his Russian counterpart, just as he only ever has words of comfort and admiration for Xi Jinping of China, Mohammed bin Salman, the crown prince of Saudi Arabia and, these days, Kim Jong-un of North Korea. When he meets tyrants and dictators, Trump – the great disruptor, the supposedly fearless straight talker – suddenly remembers his manners. If the hand he’s shaking belongs to a strongman, he bows and scrapes, unctuously deferential to the diplomatic niceties and protocols.

Only with democratic leaders does he like to play the tough guy, visiting humiliation on those nations that have stood faithfully at the US’s side for decade after decade. Russia meddled in the US’s democratic process in 2016 – as much an attack as if Moscow had launched a physical strike on a military base, as FBI agent Peter Strzok told a congressional hearing this week – but for Putin, Trump cannot bring himself to utter a harsh word.

Instead it is Britain, whose bond of blood with the US should not need spelling out, that offers up a full-dress, all-but-state banquet in Winston Churchill’s birthplace, followed by tea on Friday with the 92-year-old monarch and an itinerary that allows him to chopper around Britain pretending there aren’t crowds below who loathe him – and what does the country’s prime minister get in return? A series of insults calculated to undermine and weaken her, delivered by means of the country’s bestselling newspaper.

Theresa May should not take this too personally. Trump behaves appallingly to all democratically elected leaders and especially women, as Angela Merkel can testify: witness his public upbraiding of Germany at this week’s Nato meeting in Brussels, a tirade against an ally with next to no precedent in modern diplomacy. Afterwards, of course, Trump insisted he and Merkel have a great relationship, which only confirms both how devalued language is when it issues from the mouth of this president and the bullying pattern that is the abuser’s hallmark: a punch followed by soothing words of reassurance and the promise that things will be better in future, so long as you do as he says.

Curiously, those arch-conservatives and self-proclaimed patriots who one might have imagined to be sticklers for courtesy and diplomatic etiquette have been unexpectedly indulgent. Who should pop up on the radio to defend Trump but Jacob Rees-Mogg, who was so incensed when Barack Obama warned in 2016 that a Brexiting Britain would be at the “back of the queue” for a trade deal with the US, that he declared: “No true honest Briton is going to be told what to do by a Yankee president.” Yet on Friday, Mogg found it “perfectly reasonable” that a different Yankee president was telling the Brits what was good for them. Funny how flexible these stout defenders of British sovereignty can be. Allowing Brussels the tiniest say in our affairs would be the greatest threat to the kingdom since the 13th century. But when a sympathetic US president tells them to jump, they ask how high.

It’s tempting to think that Trump is just a mercurial, unhinged man-baby – like the blimp in the London sky on Friday – whose mood swings have to be managed: a tantrum to the Sun, then calm at Chequers. But that’s a misreading. Yes, Trump is wild and volatile, but if he lashes out it’s only ever in one direction. There is strategic method to his madness.

In geopolitics, his targets are always the same: the forces of multilateralism, cooperation and international order, whether it’s Nato, the EU, the UN or even the G7. He wants to see those bodies weakened and destroyed, replaced by a dog-eat-dog world of single states, dealing with each other one-on-one. In that world, the US would be the biggest dog, and get to snarl and snap at all the rest.

The implications for Britain as it contemplates Brexit could not be starker. The Brexiteers hold up a US-UK deal as if it’s the great prize of “liberation” from the EU. But Trump’s enthusiasm for it should give them pause. Does he really want to see us out because he wants Britain to prosper, big softie, son of a Scottish mum that he is? Or is it more likely that he relishes the chance to negotiate a deal with a needy and relatively small UK, rather than a 28-member EU with enough economic clout to sit at the table with the US as an equal?

Trade analysts say that, at most, a UK deal with the US could add 0.3% to Britain’s GDP, compared to the much bigger loss incurred by our leaving the single market. As the weaker party in talks, Britain would be under pressure to open itself up to US chlorinated chicken and big pharma.

And this is how Trump would love to deal with every country, including the nations of continental Europe. For him, Brexit is a means to the larger end of weakening or dissolving the EU altogether. That’s why he even urged Emmanuel Macron to consider a Frexit. A bloc as large and rich as the EU stands in the way of the world he’d like to see, one governed by the law of the jungle – in which the US is for ever the biggest beast.

So this is the question Britons have to contemplate, now that the reality of Brexit is sinking in. Do we want to remain in a bloc that gives us strength and safety in numbers, or walk alone into the negotiating chamber with Trump? How naive the US president must think the likes of Boris Johnson or Rees-Mogg, the pair of them eagerly willing on a future in which Britain will be the much weaker party – and imagining that Trump is encouraging this change for our sake.

More deeply, Britons need to decide where we stand on what is emerging as the defining global divide. Are we with the world that the EU, in its own imperfect way, still embodies – one built on alliances, cooperation and institutions that seek to balance might with right? Or do we want to throw in our lot with the world of Putin, Viktor Orbán and Trump, a place of jostling nations, each state alone and out only for itself, where every transaction is a zero-sum game, a world in which you either screw or get screwed? It’s clear where Trump wants us. But what do we want?

• Jonathan Freedland is a Guardian columnist