Question

Which two countries were on the side of the United States in World War 1 but were enemies of the United States in World War II?

Answer 1

Japan and Italy

Explanation:

During World War I, the United States attempted to achieve neutrality to avoid any biases toward a European-centric war; however, that was difficult. German and Irish immigrants in the USA were fighting about what was better: Central Powers or Allied Powers. The United States enters the war in 1917, assisting the weakened Allied Powers.

Central Powers: Germany, Austria-Hungary, the Ottoman Empire, Bulgaria (and other allies)
Allied Powers: France, Russia, British Empire, United States, Japan, Italy (and other allies)

The United States was involved in the Big Four in World War II. The Axis powers combatted what is known as the Allied powers.

Axis Powers: Germany, Japan, Italy (and other allies)
Allied Powers: Soviet Union, United Kingdom, United States (and other allies)

Due to Italy's changing attitudes during the war and Japan's aggression, they are the two nations who swapped sides after WWI.