Messy-co is a big ol cesspool. Always has been, likely always will be. If I were king for a day, I'd build the wall, sink it 15ft into the ground. I'd erect the thing 50ft tall, 5ft thick. On the backside, a mote filled with Louisiana gators, a minefield, rows of coiled barbed wire and trained attack dogs. Every so often, guard towers manned with 50cals.
That ought to do-r
It would be cheaper and more effective to just begin to shoot the invaders. Dead invaders are not a problem.
Fear of death will stop invasion.