That it wouldn't exist with tight border control and Mexico would probably be a decent country by now as they'd have already had their revolution and rebuilding phrase than flooding the US with immigrants as a release valve.

Look. I'm not an ethno-nat, but I'm not that optimistic about Mexico not being a shithole. It'd kinda be the first time they weren't.

The last chance they had to have a stable country died when they executed Maximilian. It's kinda a corrupt shithole. Same with Haiti. You can only do so much without imposing a coup, killing a bunch of elites, and forcibly establishing a legitimate government at the point of a gun. If you're not colonizing them, best to just keep your distance and stop helping so they can unfuck themselves over decades.