Some Mexicans in the USSA are descendants of the tribes that used to inhabit a lot of the USSA, only as tribes. There's a lot of Shawnee down in old Mexico that refused to be "resettled" at the insistence of the u.S. government. The Shawnee of course, originating in Ohio, West Virginia, Indiana and the vicinities.
I like this thread. That old dude was spot on correct.