Who will be dumb enough to believe American security promises anymore? America won't defend anyone no matter what they promiss.
If they wanted to sell defense, threatening annexation of countries they are supposed to have current defensive arrangement with is inconsistent with that. Allying yourself with Russia is inconsistent with that too.
And above all, an attempt to use past help as a reason to make the other country your colony for materials extractions while trying to sell their parts to Russia ... makes you untrustworthy.
Greenland is not threatened by China right now, they are threatened by America.
I mean, if that were the case, then their previous behaviour on Ukraine seems baffling, as it has made the defence umbrella look, at a minimum, kinda tattered. Like, we are now in a world where Poland is talking to France about hosting French nuclear warheads. If you told someone in 2010 that that would be happening in 2025 they’d think you were completely insane.
They'll tie the defence umbrella to tariffs and good behaviour.