Serious question, why don't we create a wall with a mile wide swath of Punji sticks and tire spikes? Cheaper than brick and mortar, far more effective, unclimbable, bamboo grows in abundance pretty much everywhere, easily automated for repairs in the swath (gaps that need filled), etc? Just put a sign up that says, "Enter at your own peril, you will not be rescued if you choose to enter". With this idea you could also flood the area beneath the border, which would eliminate tunneling. You can't do this with regular walls you have to use certain designs which are not cost effective.
Ethical concerns aside, people can just step around punji sticks and throw something on top of tire spikes. It's not a jungle out there. A trap that can be seen is a trap that traps nobody.
I don't think you understand how pits of punji sticks work. You couldn't easily walk through them in Vietnam, is was a field and they were like grass. Hey we're used to force movement into other areas. ^^See here An occasional 9 ft iron rod(again, easily automated) angled at 45 degrees with 6 feet of it below the ground will stop vehicles. Just put them in an interlocking pattern to minimize cost and you have a barrier virtually no one outside of pilots can get past.
A good pair of boots would have me kicking through those punji sticks in a few minutes. They're like barbed wire, no problem to get through if you've got the time and nobody is shooting at you. An iron rod? Meet my battery powered angle grinder. Again, it can only delay for a short while.
Hahaha, hahahahaha, hahahahahahaha ha. Those punji sticks pierced many a combat boot. Only a fool would believe such.
