Its not needed in many areas. Drones would be more efficient.
It is easy for the next liberal to stop surveillance (as Obama has just done), but a wall... not so much.
Any child an take a phone to the border and watch the illegals cross over. No one is stopping them and nothing happens to them after they succeed, in fact there are free services that are heaped upon them. Who wouldn't want to illegally cross the border? However no one illegally crosses over into Mexico, wonder why?