Exactly. Mexico can control it's southern border and not have to worry about them arriving and remaining there.Mexico doesn’t want them either. What nobody considers is that the caravans coming up from South America through Central America has strained some of the more civilized counties to the breaking point. A lot of these migrants will decide to stop along the way and put up their tent in one of the intermediate countries.
It’s turned a lot of these counties south of the border from Trump haters to Trump lovers. Biden has decimated some of these counties social systems and job markets.
Not to mention the effect of the human capital drain from the emigrant countries. There's a term for it I can't recall.