It would be the end of NATO if he USA attacks Greenland,USA's reputation in the Western world would plummet. Imagine if he goes like "and the Falklands,the Falklands are very strategic. Very strategic islands. And they have a lot of oil. Did you know they have oil? Yeah,apparently they have lots of oil and we must get it". Then " Grenada is strategic to us,we must have Grenada. We'll also take Iceland,they don't even have an army,they're just 300,000 people. We will protect them. And what's Norway going to do with all that oil? They're not doing anything,we need it,we're a big country".
The collapse of NATO. Which normally should have ceased to exist after the fall of communism...but...