Also, what I missed to mention is one important difference: It was built to not let people out instead of not letting them in. The actually correct analogy would be then that the wall is getting build to not let Americans flee from Trump by going to Mexico...
Hey I'm not the one who made the analogy with the Berlin wall, although I still think walls do work and work really well. Of course it is not 100% as just any other deterrent but it helps a lot if you want to keep people out and have a proper immigration system instead of mass uncontrolled immigration. By the way building a wall was the first thing the BLM/Antifa peaceful protesters did when they peacefully created their own autonomous state.