I could be wrong, but I think the US agreement with Denmark gives the US the ability to just build a new base if it wants to. He could have just done it.
I think there are 2 reasons why he didn’t go this route:
Bringing in a new state would be a big political win for him.
Greenland is rich in mineral deposits that the US can’t have without making Greenland part of its territory.
I could be wrong, but I think the US agreement with Denmark gives the US the ability to just build a new base if it wants to. He could have just done it.
I think there are 2 reasons why he didn’t go this route: