What year did the United States enter World War I?

The United States entered World War I in 1917. Prior to this, the war began in 1914, and the U.S. maintained a position of neutrality for the first few years. However, several factors contributed to the U.S. decision to enter the conflict, including unrestricted submarine warfare by Germany and the Zimmermann Telegram, where Germany proposed a military alliance with Mexico against the United States. The cumulative impact of these events, combined with a growing sentiment in favor of supporting the Allies, led President Woodrow Wilson to request a declaration of war from Congress, which was granted in April 1917. This involvement significantly shifted the balance of power in favor of the Allies.