That's the barrier Israel built between Egypt and the Gaza Strip to prevent people from smuggling arms and materiel into the Gaza Strip. That border is only 7 miles long. That wall is pretty da&ned impressive.
There are innumerable smugglers' tunnels under that wall that the Israelis have never been able to stop.
Take a look at this:
That's the US-Mexico border. It's 1,969 miles long. First let's discuss cost: In 2010 Israel decided to build another barrier along its entire border with Egypt. As per this BBC article, that barrier is expected to cost $270 million for the entire 70-mile border. That works out to about $3.85 million per mile.
Since the US-Mexico border is 1,969 miles long, that means that a first-order, reasonable estimate is that the sort of wall you're wailing for would cost at least $7.6 billion to build. Consider how well the federal government is at overspending on even trivial matters - anyone remember the $100 plus hammers in the 1980s? - that cost estimate is most likely woefully too little. It would more likely than not cost at least $15 billion to $20 billion to build the wall of your wet dreams.
Second, let's discuss how well such a wall would work in the first place. To do that, we need look no further than the very same Egypt-Gaza barrier the Israelis built. Smugglers have successfully dug innumerable tunnels under that thing and Israel has never been able to close off all of them - and that's just on a piddling little 7-mile border. Do you really think the US is going to be able to do any better than the Isaelis at preventing smugglers from tunneling under a 1,969 mile long barrier?
Talk about a Bridge to Nowhere, which would only have cost a piddling $398 million!
Can we really afford such a boondoggle - a useless waste of taxpayer money that would never succeed at stopping smugglers and illegal immigrants? - and the final cost of which would run at least $15 billion to $20 billion?
And that doesn't even start to address how long it would take to build. By the time the last mile was built, the first mile would have collapsed into dust.
Perry is only being polite when he says that such a wall would be "ineffective."