Possibly a good legal basis, those things were done differently back then. There's a lot of murky law - witness the Native American "nations" which do have many, many elements of independent countries within the boundaries of the US.

And, for a legal basis for nothing happening, try the Doctrine of Adverse Possession. For an extra-legal basis, try the Doctrine of Might Makes Right, the cornerstone of American foreign policy.

Ain't gonna lose any of those lands, though one might wish Texas could be retroactively declared a Mexican State.

As Shakespeare said in the title of a play, "Much Ado About Nothing".

Arf