In what way does the U.S. have "unchecked immigration"?

Edit: also, you have a bizarrely pessimistic view of immigrants' and refugees' potential to contribute to their host country. My parents were part of the flood of refugees that came after the fall of Saigon. Like the incoming Syrians today, they were taken in by American families and lived off of welfare for years. Now they, and their children, contribute to the nation's bottom-line, never mind the goodwill that America incurs by taking in people of need.