Despite Trump's protests to the contrary, the U.S. has an incredibly good deal with Denmark regarding Greenland right now. Denmark is responsible for the health care, food, and shelter of everyone in Greenland (which can be enormously expensive given its location) and the U.S. gets largely unfettered access to its military base there. If Greenland became part of the U.S., our national security situation would not change a bit (the U.S. would still have its base), but we would get the huge costs of maintaining a bunch of remote and distant civilians settlements. Plus Greenlanders hate the idea of joining the U.S., so the U.S. would also bear the brunt of whatever resistance develops.
The U.S. taking over Greenland over the overwhelming opposition of the locals is one of those ideas that only a total moron would get behind. That's America in 2025-2026!