The wall will work if it is manned and militarized. I am sure that legal action against the employers of illegal aliens is part of the plan to dry up the demand. Walls do work - just ask the East Germans.
Do you really want to deploy an army on the 2000 mile southern border? And the comparison to the totalitarian East German Communists doesn’t make me feel better. We have to solve this problem, but I don’t think a wall is the way. I would rather do national retinal scans as a condition to working. Or something more realistic.