I believe at the moment it's still in the "spitting on each other" phase. Had Trump actually invaded Greenland* (and likewise if he does so in the future), that's where the Rubicon gets crossed and there's no going back.

I kinda do want it to have passed that point, but not as much as I'm glad he TACOed.

* There's other metaphorical Rubicons available, this is just the one most in my mind given I live in the EU