America had tremendous economic growth from the founding up until The Great Depression, when immigration was restricted. I don’t think we should necessarily say immigration is a problem. However back in those days immigrants were left largely to their own hard work to make it. Contrast that today with about half of all immigrant headed families getting some welfare assistance (source http://cis.org/Welfare-Use-Immigrant-Native-Households).
I think it’s great to attract the best and brightest from around the world. And further to attract a population with a work ethic much higher than most native born Americans. But along with those, we are getting men and women who can’t seem to make it here either.