Greenland is not neighboring the US, it's neighboring Canada.
China or Russia can't take over Greenland as they don't have the power projection to do so, Greenland has a literal US base on it and Greenland is part of Denmark who is a member of NATO.
Also a boat landed in the US 500 years ago too so that means the US doesn't own the land either. Time to give it back to the Natives.
