Not just illegal, but legal as well.
I propose we place a moratorium on all immigration, both illegal and legal, for the next 20 - 30 years. That should be enough time to Americanize the current crop of recently immigrated folks, and to help protect the nation at a time when our Islamist enemies are crossing the borders in alarming numbers (according to a recent investigative report by Linda Vester). If we don't, our chance of surviving is very slim.