What was a major reason the US entered world war 1?

A major reason the U.S. entered World War I was the unrestricted submarine warfare employed by Germany, particularly after the sinking of the British ocean liner RMS Lusitania in 1915, which resulted in American casualties. Additionally, the interception of the Zimmermann Telegram, in which Germany proposed a military alliance with Mexico against the U.S., further galvanized public opinion and led to calls for intervention. These factors, combined with economic ties to the Allies, ultimately prompted the U.S. to declare war on Germany in April 1917.