At the end of the day, the "border" between Mexico and the United States is imaginary - a fabrication consisting of agreements, probably more than a century old, that Mexico ends at one point and the US begins at that same point. For all of the difference it makes in real terms, Mexico could begin at the southernmost portion of Virginia....or South Carolina.
Spending all of this time, effort and money to "defend" an imaginary line against impoverished Central Americans fleeing their broken countries - which we had a big hand in breaking - seems like a massive waste. It seems that the phenomenon of enforcing strict lines between countries and requiring visas to move between them is a fairly recent one. I am in favor of freer movement between countries, because at the end of the day, one point on the map is not terribly different than another one.
I know that's not a particularly popular point of view, but I think it's a less wasteful and more humane one than concentration camps and complaining about caravans and migrant moms trying to find a better home for their children.
Ringo