Look, I can understand it not being first, but seriously, do you even live here?
How many immigrants have come to the states? How many non-English foods have been integrated into the American diet and then propagated all over the globe? How many non-English forms of music have formed the basis of rag-time, jazz, rock, rap, etc, etc? How many Spanish speakers live in this country? How many Chinese, Cantonese, Koreans as well? I don't think you realize how huge, diverse, and ecclectic America's history was. The impact is unimaginable because it is so huge, it goes without saying. If you're an American, just look at your last name, chances are it's not English.
Granted, cities are generally the centers of cosmopilitanism in the States, whilst rural areas are more conservative that way, but even then, you have a huge sweeping continent with many different regions, dialects (historically at least), attitudes, religions, and Native influences.
The concept of "American Culture" is a myth.