The Wall Street Journal has an article on how the majority of the growth of the Hispanic population is due to births in the United States rather than new immigrants. My esteemed colleague has a quote in the article that neatly sums it up:
"We just have to get through this transition time," says John R. Weeks, a demographer at San Diego State University. Ultimately, he says, "the children of immigrants are going to buoy up the economy. They are going to pay for Medicare and Social Security for the aging white population."