"The Wall" at the Mexican border is not going to work. The wall represents a law enforcement issue. The people at the border don't believe it is going to work either. They believe it will fix the drug issue, it won't.

"The Wall" for the sake of "The Wall" is nothing but hubris. If the people along the Mexican border wants to stop the drug cartels, then they need to insist on having better law enforcement. The wall is not going to stop the drug cartels from carrying guns and killing people and bringing family members into addiction in order for them to work for the drug cartels. The wall will never stop the drug cartels.

It might stop some starving immigrants seeking to cross the border illegally, but, the wall will never solve the problems with the drug cartels. 

The USA military knows exactly where the drug cartels are, the routes they travel, but, nothing is ever done about it. Nothing is ever done about the poppies in Afghanistan either.

These problems can be solved, but, no one bothers and a wall is not going to either.