We would see exactly what people in the US have been dealing with for 10 years. Everybody would wring their hands and say "unbelievable!" and then nobody with the actual capability to do anything about it actually does.
The entire world is just rooting for Father Time on this particular problem.
If the US actually did invade Greenland it would mean the end of US Europe trade and cooperation as we know it and the end of NATO (and likely UN). China would suddenly be the main trading partner, also in military equipment. It would be the end of US as it is today.
The entire world is just rooting for Father Time on this particular problem.