It's also worth remembering that this used to be a rare phenomenon. What made it common was not a new avalanche of people coming to the United States without permission. It was a federal offensive to intercept them in major border cities where they used to arrive.
"Closing the old entry points diverted them into places which didn't have many undocumented immigrants before," Princeton University sociologist Douglas Massey told me. Instead of sneaking into San Diego or El Paso, they are prone to entering somewhere else -- often in the Arizona desert, where the chance of being caught is lower.
Turning the border into a 2,000-mile replica of the Berlin Wall may sound like a simple cure for the problem. But besides being hugely expensive, it would have effects the advocates would not relish.
How so? Massey says the number of people coming illegally has not risen appreciably in the last couple of decades. But the number staying has climbed, because anyone who leaves faces a harder task returning.
Had the government not cracked down at the border, he says, "the undocumented population would be half what it is now." A fence intended to keep illegal immigrants out is serving beautifully to keep them in.
Assigning local police to enforce federal immigration laws would also have unhealthy side effects. The Major Cities Chiefs Association, representing 56 police departments, says it hinders law enforcement by deterring members of immigrant communities from cooperating with cops.
Last year, Police Chief George Gascon of Mesa, Ariz., (now chief in San Francisco) told a congressional committee that in some cases, this approach "is setting the police profession back to the 1950s and '60s, when police officers were sometimes viewed in minority communities as the enemy."
If there is anything we've learned about getting tough on illegal immigration, it's that it rarely works as intended. Like punching a wall, it may feel good for a moment, but it hurts a lot longer.