President trump recently offered President Lopez-Obridor of Mexico military assistance in dealing with the drug cartels that currently run the country, and the offer was refused. Why, do you suppose? Well it's like this; The cartels do in fact control Mexico much like the many little duchies used to control Europe, each one with its own borders, army, and prince. AMLO knows this as does everyone else, presumably including all the Dem candidates who are advocating for an open southern border. The cartels are willing to let him claim to be president of all Mexico as long as he doesn't think he's actually in charge of any of it.
Thus, AMLO is in bed with the cartels, whether he wants to be or not, and he understands that if he tries to get out of bed with them, he won't make it to the door. When El Chapos sons were recently arrested and turned over to the army, the cartel immediately rolled out their own armor and troops, better armed and equipped than the national army and attacked on two fronts, first pinning down the regular army, and at the same time opening a second front which visited the soldiers homes and began killing their families. The army anticipated this and had begun moving the families from on-base housing to more secure locations but not before significant casualties were inflicted.
This seems to be the current state of the state in Mexico. New cartels have sprung up specializing in people smuggling, which the narcos allow to exist as long as they don't try to expand into drugs. As the "refugees from Africa, the Middle East, China, and how could I forget, South and Central America arrive at the U.S. border, they are taken in by the cartel controlling the section of border they happen to bump up against, and hustled across the line.
Effective closure of the border to this sort of thing, possibly along with a reduction in the drug flow will probably result in more aggressive techniques for moving things, possibly involving use of the cartel armies to breach the border and deposit their products deeper inside the U.S. The last time something like this happened, the end result was the Treaty of Guadelupe-Hildago which established the current U.S. -Mexican border. The next time I suppose we might wind up owning all of Mexico, which at this point we could probably do with out. Perhaps we could just inform Mexico that the border was now 200 yards south of its present location, and the strip of land we take will be used to build a roadway with a big wall/fence on the south side of it, thus eliminating the requirement to buy or appropriate any land from American citizens.
Someone should ask the Dem candidates which of the cartels they would turn over control of their newly erased border to and how far north they will tolerate the advance of the narco armies.