You missed the central point of my piece: In a very short time, "most Texans" will BE mexicans. When that occurs..."most Texans" will NOT fight as you suggest, but rather will enthusiastically agree to be reunited with their homeland (which, as they see it, is the legitimate owner of Texas to begin with). At that point, the US will have one of several options:
1) Let them have Texas (hopefully with the preconditions that I mentioned before)
2) Fight an ongoing West Bank-style conflict, with soldiers from Indiana and Oregon chasing mexican rioters and guerilla fighters through squalid barrios under a hailstorm of rocks, molotov cocktails, and occasional pistolo fire.
3) Some form of demographic reversal (how is THAT for a delicate euphemism?)
4) Just to give the liberals their due...perhaps everyone will live together in love and peace despite the differences. The new Hispanic majority will treat the white minority there will love and respect...and they will eagerly become productive, law-abiding American citizens. In which case, the titanic demographic shifts in the SW will not affect geopolitics (this is never how history works out...but what the heck? there is a first time for everything)
I don't agree with your premise at all, and don't see it happening. Texas and Mexico are tied together by history, and by a common border. I don't know what your vision of Texas is, but it doesn't seem to be anchored in reality. Feel free to offer up your own state to Mexico, but leave us out of it. We have peacefully co-existed with our neighbor to the south for quite a long time. Our problems are not unsolvable.