Pakistani and Egyptian immigrants pledge allegiance to the United States during a citizenship swearing-in ceremony, Aug. 2004.
Only about one-third of Americans say the country has a basic culture and values that immigrants take on. Nearly twice as many say our culture and values change as new people arrive. But two-thirds of non-immigrants say America should have a single culture. Is America a melting pot, a salad bowl — or, as one Harvard professor puts it, tomato soup? NPR's John Ydstie reports.