It is very effective, and those who would tear it down would be exposed as traitors to America.
What would be your opinion if the cartels decided to use their weapons and explosives to make holes in the wall?
Kill them with overwhelming force.
What would be your option?
Okay, you can kill them with overwhelming force. But, what if they decided to blow a hole in the wall when there was nobody around? How would you catch them then?
You are making the assumption that there won't be surveillance on the wall 100%.
Tell Me, how does any law enforcement agency determine how something is done? Or are you saying that forensics will cease to exist when we build the wall?
No, I'm not assuming anything. I do know however that you won't be able to have people who would be able to quickly respond to something like that if it was in a remote area. All the cartels would have to do is watch and see what the routine for patrols is, and wait until there was a gap, and then use explosives or an RPG to blow a hole in the wall and then boogie.
The only way you could track someone who did something like that is if you had eyes on them when they did it and kept them on them until you caught them.
And, forensics generally only tells you how something happened, not who did it.