Would we lose, though? I keep seeing this, and I'm not convinced it would be that clear-cut, unless I'm missing something?
I get that the US has the biggest, singular armed forces in the world, but they wouldn't be fighting a single army. They'd be fighting the EU, which includes other powerful armies such as France, Italy, and Germany.
I wouldn't rule out the UK not joining in some description, given our proximity to the EU and working relationship with them, plus the damage to our economy and EU relationship if we refused to help if asked.
And then there is Turkey, who have a reasonably powerful, well-funded, and well-trained military. They're a close ally of the EU and could use cooperation in defending Greenland to strengthen their chances of becoming a member. I'd put money on them offering to help if it came down to it.
Individually, the US would decimate each of these forces, but when combined, I'm not so sure that they wouldn't have enough manpower, hardware, and funding to easily defend against the US.
I'm doubtful it would come to this, not 100% sure it won't, but hopefully optimistic that even Trump is not insane enough to risk the destruction of Nato and war with the EU over a country he already has access to. If it turns out he is, I am 100% convinced it will be the start of WW3.