Which country did the United States fight against during World War II?

The United States fought against Japan during World War II, particularly after the Japanese attack on Pearl Harbor in December 1941. This act of aggression prompted the U.S. to formally enter the war, leading to intense battles in the Pacific Theater, including significant events such as the Battle of Midway and the island-hopping campaign.

While it’s true that the U.S. also fought against Germany and Italy (as part of the Axis Powers), the question specifically sought to identify a country, and Japan was a significant adversary that contributed heavily to the conflict's scope, particularly with its actions in the Pacific. Moreover, France was a part of the Allied Powers and was occupied by Germany for part of the war, making it an ally rather than an enemy in this context. Thus, selecting Japan highlights one of the primary aggressors the U.S. faced during World War II.