Is not helping making potential emigrants want to stay home the best wall?
Is not the wall that America and Mexico might both want, that which separates us from those bad robots taking our jobs? :-)
What if a country attracted Americans like America attracts others? Would there be a Berlin Wall to keep Americans in?
Whatever, if Trump waves bye-bye to Nafta, I guess he knows that in order to achieve some of what he wants to achieve with the Wall, the Wall has to be at least twice as high.