I want to point out, that, throughout history, there has been a particular country that has built a gigantic border wall.
And it failed, miserably. The mongols had no trouble invading the country even with a massive wall.
Also, in modern times, more foreigners, now cross, step on, across, take pieces off the wall than ever before.
I think you've hit on a great idea, G-Man. We build the wall. It becomes a great tourist attraction. We make it a national monument. We charge admission for people to touch it, kick it, etc. We recoup the $5 Billion. If we charge $5 per person, and we get 10,000 visitors per year, that would be $50,000 per year, and it would only take..................never mind.