Why did the U.S end it's neutrality and enter the war?

The U.S. ended its neutrality and entered World War I primarily due to unrestricted submarine warfare by Germany, which threatened American lives and commerce. The sinking of the Lusitania in 1915, along with other merchant ships, inflamed public opinion against Germany. Additionally, the interception of the Zimmermann Telegram, in which Germany proposed a military alliance with Mexico against the U.S., further galvanized support for entering the war. These factors combined to shift public sentiment and political will towards intervention.