Correct, but the world is divided into nations already that use up 100% of the claimable useful territory. I can't imagine a non-violent process by which the United States carves up a chunk of Montana and goes "here you are separatists; have fun."

That'd be inconvenient for the Montanans that own that land.

... and the US has some historical precedent regarding how it responds to separatists in general that isn't very promising. ;)