Not only that, but the socialist Americans of Mexifornia would have to move, cause according to Mexican law, no foreigners are allowed to own property with in what, 25 miles of the coast? Oh and they can't engage in politics, so they're screwed there... Of course they loath anything military so no problem with them wanting to join the mexican army, not that they could according to mexican law.
If we gave it back , we would see Tijuana-like enclaves replacing all the major southwest cities. AND we would have to deal with "immigrants " sneaking into Des Moines