Most people in Greenland want Independence from Denmark. They consider themselves foreigners to the country and yet devour 0.6% of their surplus.

IMO it is foolish both for USA and Denmark to take them. Cut them loose as they desire and let them trade their minerals which they will surely do as soon as they realize their free lunch is gone. You would still get the thing you want it for, the greenlander are happy they are free of the colonizers, and it likely wouldn't change things militarily as they would absolutely sign a defense treaty as soon as you hand them the pen.