It may stop the remittances, which may get Mexico to move it’s butt, but illegals will still get here any way they can. I’m sure there’s a regular underground railroad of people going back and forth. They’ll mail it or hand carry it, if they have to.
As said there will always be illegals trying to get to the US.....however what we’ve been seeing these past years isn’t just illegals wanting to get here...it’s far more than that.