If you have these watch towers every several miles, with cameras surveying in between, it would be nearly impenetrable.
That Israeli wall wouldn’t do jack squat out in the desolate desert of the US/Mexico border. Too easy to get over. The Israeli wall serves the purpose of not allowing car-bombs to drive in at will.
If you had guard towers with orders to shoot on sight there wouldn’t be any problems.
It does stop terrorists traveling by foot.
If you have these watch towers every several miles, with cameras surveying in between, it would be nearly impenetrable.