Right now there are more people leaving the US than entering, so I think it's more to prevent people from escaping. You know, like North Korea.

Or ladders, or rope, or digging, or the many other ways they have bypassed and overcome the new sections of wall already.

The whole approach is so backwards. The drug war and neocolonialism have pushed many of USA's problems to Mexico, so many Mexicans wish to move to the US to escape those issues. Best solution: legalize and regulate drugs, treat your addicts, help Mexico to put down the cartels, and work to build a tight friendly partnership with Mexico - a very significant trade and cultural partner with a huge shared border. Win for everyone, immigration plummets. Selected solutions: built an enormous wall, lambast their leaders, threaten invasion. Republicans are still in a 7th-century Chinese solution mindset, 1400 years later. Oh - and pour $30,000,000,000 into your secret police force to find and deport any suspected South American or Mexican-heritage people, primarily without trial, seemingly hurting just as many US citizens as new immigrants - shouldn't forget that brilliant strategy.

If the US could just stop shooting itself in the feet the wounds might heal.