It won't matter. You could send back all the illegals, and the Hispanics would still, eventually, outnumber whites. Whites are simply not reproducing, or even marrying, at previous numbers.
Gee. And that matters why? China and India outnumber us signicantly as well. That just means that there are more starving and/or poor people over there than over here. They can outnumber us all they want to... in Mexico. That's not going to spell dominance.