"European leaders are telling President Trump they'll support him in prioritising Arctic security, so there's no need for him to go it alone over Greenland..."
Playing along with the whole security pretence shit...as if it's actually real will get them nowhere.
Trumps only interest is to go down in history as someone who did something "Big": so big his farcical presidential reign can't be forgotten. Greenland: a huge snowy empty waste with little to no security issues that aren't already covered, but which has the capacity to burn huge amounts of US resources and provide absolutely nothing in return on the "investment" for many decades... is at least very, very "big".
With Trump discussing things in terms of real issues is complete a waste of time. You've got to think the situation through the mind of a spoiled five year old child: which is effectively what you are dealing with. He wants a very big toy: Someone else has it. He cries and kicks and screams...do you take the toy from someone else to give him what he wants?
And then what? He moves on to the next even bigger toy of course.
In the larger picture the real issue is the systemic failure of the US political system: checks and balances which should be there to stop a mentally and emotionally undeveloped individual from holding a pivotal position never mind carry out a vitualy Imperial rule by "decree" have totally failed or been deliberately & fatally undermined.
The Republic is Dead...it's no wonder they are calling him Caligula.