There have been many different waves of immigration into the country, starting with what we call the Native Americans. They were originally a tribal people who fought against and were allied with each other for hundreds of years. They were almost all subjugated by European immigrants that came in the 1600s. Some of the first European immigrants were religious refugees who fled their homeland seeking freedom.
Today our culture relies heavily on romanticizing military victories, cowboys, and our allegedly strong sense of individualism. We love buying things, and despite not having the largest percentage of the population in the world, we have one of the largest economies.