I Don't Think R's Realize the Effects of Greenland Joing the US
First off, Greenland can leave Denmark anytime according to their laws, I just want to get that put of the way. 2nd Greenland likely wouldn't join as anything less than a State, giving them 2 Senators and House members, all of which will probably be Democrats. The whole reason Greenland wants to join the US (the amount that does at least) is for investments, which you really don't get from being a territory (look at PR for a reference).
All of this is ignoring the fact that if we make Greenland a State PR will likely become one with it as Dems won't give the necessary votes otherwise, and they've voted for Statehood enough times now, so we'll need to placate them.
EDIT: Spelling and paragraph break up