Walls don't work and the US led the chants against the wall in Berlin.
Can you backup your opinion with subject matter experts and empirical proof and statistics?
Great Wall of China never stopped an invasion.
OMG, don't you check anything? You just make shit up! If you can't debate properly, just read the posts.
Was The Great Wall of China Actually Effective?
"Did the Great Wall actually succeed in keeping enemies outside China’s borders? The short answer: yes, the Great Wall was successful in keeping semi-nomadic invaders out, which was the primary concern at the time. However, the wall did not stop some large scale invasions, and even the nomadic people were able to breach the wall from time to time."
The wall was generally effective, but not 100% effective, which is fine. Its way better than an open border.