The United States of America (also referred to as the United States, the U.S., the U.S.A., or America) is a country primarily located in North America. It plays an important role in the Call of Duty series by having American soldiers appear in every Call of Duty game. World War II campaigns provide the setting for the first games until Call of Duty 4: Modern Warfare. The United States flag is also seen in Call of Duty: Heroes as a decorative item. The United States is the only country to be featured in all games of the Call of Duty series.