Which major event shocked the American people who led Wilson to no longer call for peace?

The major event that shocked the American people and led President Woodrow Wilson to abandon his calls for peace was the interception of the Zimmermann Telegram in early 1917. This secret communication from Germany proposed a military alliance with Mexico against the United States, which incited public outrage and fear of German aggression. Coupled with Germany's resumption of unrestricted submarine warfare, these developments shifted American sentiment towards supporting entry into World War I. As a result, Wilson called for a declaration of war against Germany in April 1917.