Is this a joke?
There is no reason for Greenland to be part of the US. They don't want to be. They aren't culturally American. They're not geographically close.
It's geographically close to Canada. If Canada wanted it, it would be worth discussing.
The only way that would make sense to the US would be exactly what the article doesn't say: buying it. If we want its mineral wealth or strategic position, we should pay for that. Let capitalism do its work: pay the Greenlanders each a million dollars, and have them vote to join the US. As citizens, and a state of their own -- it's much smaller than any state, but they're not going to submit to taxation without representation.
That is not really how these things work. "Pay the Minnesotans 1 dollar each and let them vote if they want to join Canada".
Yes, I know what that implies about the Civil War.