As much as I like the idea, and the spirit of this comment, I don't know if it's fair to make Mexico take responsibility for a state as back ass-wards as Texas.
We've spent the better part of 200 years arming a bunch of white settlers while letting them circle jerk themselves raw over mythical Texan exceptionalism and Evangelical Christianity.
Giving Texas back to Mexico, is like feeding a toddler a pound of sugar, giving it a knife, and dropping it off at daycare.