Regarding what @LifeExperience posted, which is only just upthread, it's long so I won't repost it- I think they are right in a lot of ways.
I can entirely see why the US wants Greenland; we have already seen
many places that were tacitly either pro-ish the west, or neutral now rabidly in the hands of Russia and China, like much of Africa. We can be sure that if Starmer gifts the Chagos Islands to Mauritius, for some odd reason, we will see a Chinese military base on it within a few years; China has got very strong infiltration into the Panama Canal, and Russia and China are very much eyeing up the northern sea route. Control of Greenland would be a major step towards this.
I believe the US look at Europe and see still jingoistic but sclerotic nations hand-wringing their ineffectual, inclusive, red-tape bound way to future poverty, increasingly dependent on young 'aliens', a certain percentage of whom do not share our cultural views, to function; the US do pay to defend Western Europe from Russia, while Russian influence creeps gradually westwards, again. The peoples of some border lands want to join the EU so the EU will defend them from the bear, and they can get a job in Germany. They want the western leg-up which the established Western Europe expect for the US.
Russia will win in Ukraine, but they'd win tomorrow if they wheeled out their Big Guns. We'd say 'but we'd counter them, using our Big Guns'- but what we'd mean is 'America will save us!' British military top brass have already openly said we barely have the wherewithal to defend ourselves right now, let alone defend others.
I think the US has lost its sense of pride, some of it rather overblown, I have to say. The west doesn't aspire to be American anything like it did 30-40 years ago, but that does explain 'Trump', and that if Western Europe has lost its sense of respect, if not awe towards the USA, the USA might feel less inclined to defend us.
Trump is right to demand we pay up for our defence. And in this vein, the US are right to support Israel in the Middle East, a small island of western sentiment awash in a sea of medieval Islam whose peoples either want Death To The West or a Green Card....