For the French, Tahiti has as much standing, as much French citizenship, rights, obligations, etc, as Tours, or Lyon, or Deauville, or Nancy, or Toulouse, or oh ... I could go on and on. It is regarded as a French Departement, exactly as any Parisian suburb, as any French city, or town, or district.. It has representation in the Elysee, the French parliament. ( Tahiti sends two parliamentarians, elected in Tahiti )..
Greenland has something similar, although much much older in tradition , in settlement, in attachment to Denmark, it goes back to the 14th century, and has continued without break ever since. Which is 3 centuries more than the French in Polynesia. France still has an outpost in North Africa, Djibouti, a French Foreign Legion base, but it steers clear of much of Africa , after Burkino Faso removed the French....
The tyranny of distance is the overriding factor, as you point out.. For the French, maintaining Tahiti is a matter of pride and sensibility, no matter the cost, for the Danes, Greenland is family. Old established blood tie family, and that is a hard one to sever, particularly as neither wants to do that. That does not look like changing any time soon. There is no reason for the Danes to change it's perspective of Greenland, and it seems the appetite for separation is rather muted at the moment from the Greenlanders,.. not surprisingly.
Trump will have to go to war, in all it's madness, because it is not something the Danes, or the Greenlanders will give up voluntarily . Any fool could see that a mile off.