What was the reason America entered the world war 1 on the allied side?

America entered World War I on the Allied side primarily due to unrestricted submarine warfare by Germany, which threatened American shipping and lives, exemplified by the sinking of the Lusitania in 1915. Additionally, the interception of the Zimmermann Telegram, in which Germany proposed a military alliance with Mexico against the U.S., further galvanized American public opinion. Economic ties with the Allies and a desire to promote democracy also motivated the U.S. to join the conflict. Ultimately, these factors combined to shift American sentiment towards intervention in the war.