...and it's a damn good thing; otherwise, the pobrecitos would be crashing the fences to get from what is now Texas, N.Mexico, Arizona and California, in order to get to all that prosperity in Oregon, Utah, Colorado and Oklahoma.
Move Mexico north, move its inherent lackluster perforance, rampant corruption and concommitant poverty north. They are clueless.
Good parts of Oklahoma and Colorado were parts of Texas.
Imagine the hand-wringing from Fox and others if many Mexicans were drowning trying to make it across the mile-wide Mississippi. They should wish we'd take over the rest of Mexico too so they wouldn't have to die making it across deserts and the scrawny Rio Grande.