What were the factors that led to the US' entrance into World War 1?

The United States entered World War I primarily due to several key factors: unrestricted submarine warfare by Germany, which threatened American lives and shipping; the sinking of the Lusitania, a British ocean liner with American passengers; and the interception of the Zimmermann Telegram, in which Germany proposed a military alliance with Mexico against the U.S. These provocations, coupled with a growing sentiment in favor of supporting the Allies, ultimately pushed the U.S. to declare war in April 1917.