Karen plays a woman that is maintained by her black lover. He allows her no freedom and demands that she be available whenever he desires her. Karen finally realizes that this is not the life she wants. but she doesn't know how to break away from it. While at the beach she meets Richard, who is a porn star. He explains that there is no difference between them except he is paid for what he does and he still has his independence. They hit it off immediately. Richard's words give Karen the courage to break away from her controlled life and go into the porn business. As fate would have it, her first on screen job turns out to be with her star struck lover, Richard!

Documentaries were the first types of films to break through the hardcore feature barrier in 1969. SEX U.S.A. highlights the frank, open, and revolutionary sexual attitudes of the time.