Which countries did the United States primarily fight against in World War II?

The United States primarily fought against Japan, Germany, and Italy during World War II because these countries were part of the Axis Powers. Germany, under Adolf Hitler, was engaged in aggressive expansion across Europe and posed a significant threat to Allied nations. Italy, led by Benito Mussolini, was allied with Germany in this expansionist agenda. Japan launched attacks in the Pacific, notably the attack on Pearl Harbor, which led to the United States formally entering the war.

The focus on Japan, Germany, and Italy as the main adversaries of the United States in World War II is grounded in their roles as aggressor nations that challenged international peace and stability, leading to a widespread conflict involving many other countries aligned against them in the Allies' efforts.