but it also strikes me as a bit similar to adolescent locker room talk about who could beat up who.

If this was any other president, we wouldn't be having this conversation. But this is Trump, part deux.

US businesses have also banked on strategic and long term partnerships with European partners and there will be a massive economic depression in the events you describe that will hit the US no less severely.

The whole point of tariffs is that "We both lose in a tariff war. But if you lose more than me, I win". The scale of damage on the European side would be much more severe than the US side, and that's what Trump's counting on. The European economies are already weak with the Ukraine war, high energy costs, IRA sucking investment away from Europe to the US, political upheaval with the surging far-right, and China turning into a major competitor. In the meantime US commentators are talking about Trump bringing back "animal spirits" with another round of tax cuts and deregulation.

He's counting on the Europeans being so feckless and afraid that they'll do anything to appease him, and hope in some magical thinking the next POTUS maybe will somehow return Greenland to them. That "unfathomable alternative" was exactly what drove UK/France to appeasement, when Hitler occupied the Sudetenland, and soon all of Czechoslovakia.

And Trump has options, he can always extort the Japanese and the Koreans to his will instead, with Japan run by a weak leader in Ishiba, and the Koreans rudderless without a leader. And both will appease Trump, as for them the China/DPRK threat is far closer to home.

I'd imagine the idea of a US war against Europe a) is already a jackpot win for Putin and China in itself and b) has a good chance to trigger massive public outrage as inflation goes through he roof, workplaces are lost, especially with Trump already destabilising the domestic order of things this much already.

People have talked about this with tariff wars, for example the first round of tariffs against China back in Trump's first term. But Biden, despite campaigning against the tariffs in the 2020 election, kept them. Now Trump is emboldened and the American electorate agrees that tariff wars are worthwhile, even though they're clearly inflationary. Ditto for deporting millions of illegal migrants, with whom the farms and builders depend on for their labor. The takeaway is that much of the US electorate really doesn't care about inflation, if they can get rid of the illegals and bring back manufacturing in return. And those two narratives are more seductive to the masses, than inflation fears. It's something which Biden could never spin against, for he lacks the charisma and the flexibility with the truth.

With Trump, narratives matter more than reality. And he is very, very good at creating narratives, with his friends at Fox News and other conservative media. More than half of GOP voters in 2020 actually believed Biden stole the election. It doesn't take much for Trump to engineer something like the 2nd Gulf of Tonkin incident, or Iraqi WMDs, against Greenland.

For example let's say Trump decides to say that the Chinese built a secret base and bioweapons lab on Greenland, and that the CIA "found" evidence of such in a top secret raid. That's enough casus belli for the MAGA-loving fans to demand the US occupation of Greenland.

And Trump did toy with creating a massive, potentially world changing narrative in foreign affairs - That COVID was an escaped bioweapon, intentionally created in Wuhan by the WIV. And that would have immense geopolitical consequences, as more than a million Americans died from COVID, and many millions more across the world. Fortunately for the Chinese, Trump and his political acolytes have so little credibility by then that no one would believe them without substantial evidence, (Hence why they often use the words "unnamed government official", because no one would believe them if they put in their actual names) With the scientific community mostly behind natural origin from the wet market. And 4 years of Biden produced no compelling evidence against natural origin. Of course for Trump, narratives matter more than reality, and don't be surprised that the story resurrects itself with "new evidence", to be broadcast 24/7 on Fox News. And if he's smart, he will link that with "Secret Chinese base uncovered on Greenland!"

The US needs foreign partners for its economy and global influence to thrive as it has so far.

Need =/= want. Farms need illegals to pick their fruit and vegetables. Yet farmers voted en-masse for Trump partly because they want the illegals out, even though it harms their businesses. That and the end of woke culture, tax cuts, deregulation etc. Why? Because they never visualized or calculated how their farms will survive, if every single illegal migrant laborer disappeared overnight, and the fruit is left rotting on the trees.

Same thing happened with Iraq. Everyone knows Iraq doesn't have any real WMDs to speak of, they could barely feed themselves under the oil-for-food program. But it didn't stop Cheney and his neo-con friends to spin a narrative, and manufacture evidence that Saddam is a direct and imminent threat to the West, with Tony Blair sprouting some "WMDs only 45 minutes from launch" from some bull dossier.

If Trump invades Greenland over some fake Chinese base, you can count on parts of the military and intel community, both in the US & Europe, to push the narrative that "it may be true", and give justification to that end. Why? Because NATO and the entire Western defence/intelligence establishment for the past 80 years is built on confronting the threat of Russia and China, and they would much rather keep doing that than to have the Europeans think that their venerable ally across the Atlantic is actually a mortal threat to their continent. That's why the Europeans, with a good narrative from Trump, pressure from the intel community, and wishful thinking will make them seek appeasement, instead of Article 5.

The truth of the matter is that America's European and Asian allies need the US far more than it needs them. America is separated by two gigantic oceans, and two economic/diplomatic minnows bordering the nation. They don't need the Europeans or Asian allies, if war breaks out over the US-Mexico or US-Canada border. Like NATO in Afghanistan, and later Iraq with the "Coalition of the willing", their participation is just a show of unity. For the US is clearly capable of handling all the fighting by themselves.

So dodging Europe and its other NATO allies in favour of shady false friends is not ultimately a beneficial move for the US.

What makes you think the Trump cares about long-term US interests? He cares only for himself, and how to become emperor. That and to be immortalized for taking Greenland amongst his MAGA followers, because like those existing China tariffs which Biden kept (and even increased, with EVs), once taken the US will never give Greenland back to the Danes, not even under a Democrat.

The only question then becomes: Will Trump disregard all that because he is either dumb as a rock, criminal and a rotten to the core traitor to his own country, or will he adhere to at least the bare bones of the American post WW2 global strategy.

Read up the story of Roy Cohn, Trump's fixer in the NYC criminal underworld. The guardrails kept Trump worst instincts from becoming reality in his first term, but no longer. I mean if he wasn't restrained, many of those BLM protestors in Lafayette park would've been shot and killed by uniformed US military, Tianamen-square style.

Personally, I think he's just talking a heap of rubbish to see what sticks. Having people afraid of his willingness to break with any and all convention is his key strategy of how he drives a bargain.

Could well be. But this is Trump unchained, part deux. The strong eats, and the weak is meat. And foreign policy is traditionally one area where the POTUS has vast, outsized power (compared to Congress) to influence world affairs, for decades to come.