Walls are stupid and offensive symbols and practically useless for the purpose of keeping people and contraband out. People can go over a ladder. Contraband can be launched over any wall by the ancient Greek siege machine, the catapult, which can be made by anyone, anywhere. Or carried by drone aircraft.
A border wall would be ecologically a disaster, restricting animals common and rare in their necessary mating and feeding travels. A border wall would be an impediment to commerce, mostly legal (see catapult for drug transport.). The wall would have to be monitored with expensive technology, drones and remote cameras with transmitters. The cost-benefit ratio would be absurdly high. Talk about the idiocy of paranoia! And still, determined smugglers and terrorists would find a way in. America, gather your courage! No matter what, all of us will die sooner or later.

And guess what - US taxpayers will pay for the abomination.