We should construct a $100 billion dollar Super Fence armed with heating-seeking missiles and computer controlled dual mounted 50 caliber machine guns
Anyone getting within 500 feet of the fence without a reason to be there would be instantly vaporized. Naturally, we would have to have a couple dozen legitimate entry/exit points in order to conduct trade and commerce.
Then we would have to demand that everyone have a National ID Card in order to use the National Monetary Exchange System (or whatever they called mandatory debit cards).
Only criminals and illegal immigrants would still be using cash.
We round up the cash users and those without National IDs and simply execute them after giving them a year to argue their case. If they succeed in proving they are worthy of being US Citizens, enlist them in the army and give them their Passports, National ID Cards, and National Monetary Exchange Card after a year of service
Leave a couple of large holes in the fence for them to sneak back across the border through. Don't harrass these people. If the Mexican government feels like doing something about them, it's not our problem.
Periodically we would have to move the bodies out of the way with bulldozers. Give amnesty to a few illegals who feel like working for the government as dead-body removing bulldozer drivers.
And for those who don't feel like living in a Police State/Neo-Stalinist Regime....
Maybe just give permanent resident status to those who haven't been causing any trouble, kick out the trouble makers (I don't care where they end up), and hire enough border patrol agents to eliminate illegal immigration and drug smuggling. Lastly, legalizing marijuana would have a dramatically positive effect on the border situation.
Just my two cents...