It's not yet a full year since European leaders buckled up for President Trump's second term, and now this rollercoaster ride feels it has reached its most dangerous turn yet.

The occupant of the White House is dangling the threat of economic punishment over the heads of countries that are supporting the territorial integrity of an EU member, Denmark.

Leaders will hold an emergency EU summit about this in the coming days. If the European Union fights back with similar countermeasures, then it risks a full-blown trade war with the US.

If it doesn't take action, will Trump conclude the bloc of 27 is weak, divided and too scared to stop him carrying out his threat of obtaining Greenland – either by buying or taking it with military force?

French President Emmanuel Macron says it's time to use the EU's "trade bazooka" for the first time. This is the Anti-Coercion Instrument (ACI), which would allow Europe to hit back with counter-tariffs, restrict access to the Single Market and block applications for lucrative EU contracts.

There is a great irony that this weapon was originally designed to combat any bullying interference from a hostile external power.

They were thinking of China, not the US.

In the here and now, some EU leaders are weary of the Macron approach. Among them is Italy's Giorgia Meloni, who has enjoyed a better-than-most rapport with Trump.

She has spoken of a "problem of understanding and communication" over the recent sending of troops to Greenland by some European countries, including Denmark, but hasn't expanded on what may have been misunderstood.

If the intention was to placate Trump and suggest he is absolutely right that Arctic security must be stepped up, the sight of those soldiers only seemed to provoke him into making his latest threat.

Meloni's explanation of something lost in translation opens the door to a more diplomatic approach to tackling this precarious EU-US crisis.

Sunday's emergency meeting in Brussels of EU ambassadors was a discreet affair, unlike the routine top-level summits where the traffic stops, roads are closed, and leaders stream towards the cameras to deliver their thoughts.

It's not clear who will make the next move and whether Trump will take some heat out of his latest threat or, in fact, double down on it.

EU action on something so sensitive is unlikely to be swift and unanimous.

Europe has tried to placate President Trump in his second term as best it can. Some have called it shrewd, others sycophantic.

But now, there's a distinct feeling he's not just pulling up the Transatlantic diplomatic drawbridge, but is threatening to blow it up altogether.