Odds and Ends
16 8, 12:32pm
It's because America is a country of immigrants. If you look in your family tree far enough back, then you'll find an ancestor from a foreign country who left in search of either economic opportunity or escape from persecution (in some cases, such as Ireland and Armenia, "persecution" translates to "outright genocide").
One thing Americans pride themselves on is having ancestors who came to this country with nothing and built a life for themselves (that's why America is sometimes called "the land of opportunity").
Even before there WAS an America, the thirteen colonies were populated by people fleeing religious persecution (Puritans in Massachusetts, Catholics in Maryland, etc) who had many different backgrounds and came from different parts of Europe.
Though when talking of their heritage, most Americans will refer to themselves as "German-American" or "African-American" or "Japanese-American" instead of simply "German" or "African" or "Japanese".