You'd have a point if the Concertina wire were only at the top of the fence instead from top to the bottom of the entire fence.
I think it could be improved with the modifications I suggested. It could also use 100 foot observation towers (armed with remote controlled .50 caliber machine guns) spaced 1000 feet apart to monitor the situation.
I could go on but I don't think we're serious about border control until we implement something like it.