Ok this is a very simple solution to a complicated problem. Most likely my fellow conservatives would disagree with me on this one. But here's what we do:
Everyone in the U.S. as of today is allowed to stay and is granted citizenship. What's 5 million more people? Not that big of a deal. So, we are all given passports. We put up a fence around the borders with machine gun nests and maybe even a moat. No one gets in or out without a passport. And we document everyone that is here from Mexico and Canada. If we find you in the U.S. and you are undocumented then you have to go home immediately. Everyone here now is happy and we head off the rest at the pass.
Either that or we make Mexico the 51st state and we tax them to no end. j/k but at least we'd rake in the pesos that way.
Either way we have to do something. I'm not singing the national anthem with a Mariachi band and accordions.