What two events brought the United States into war?

The two key events that brought the United States into World War I were the sinking of the British ocean liner RMS Lusitania by a German U-boat in 1915, which resulted in the deaths of American passengers, and the interception of the Zimmermann Telegram in 1917, in which Germany proposed a military alliance with Mexico against the U.S. These incidents shifted public opinion and led to the U.S. declaring war on Germany in April 1917.