According to some negotiations back in the day between America and Mexico, Mexico allow you to have Texas and the other states while you allow crossing boarders for free. And since Mexico has some sort of open boarders allows no citizens to walk their journey freely from the south to the north. Now both countries are facing the same influx of immigrants. The bad shit is Mexico cannot modified that decree since is like trying to modify 2A 😬 unless USA returns those lands to Mexico I don't really know about this part but this is what it is.