The United States entered World War 1 when they had a note given to them from the British that was from Germany. It was a note to Mexico, called the Zimmerman Note. Germany promised Mexico the land that America took from them earlier (like Texas and Arizona) if they helped Germany win the war. read more
On April 6, 1917, two days after the U.S. Senate votes 82 to 6 to declare war against Germany, the U.S. House of Representatives endorses the decision by a vote of 373 to 50, and the United States formally enters the First World War. read more
The United States entered World War I in 1917 because of the attacks that were occurring on American ships by German submarines. Additionally, Americans were enraged that Germany sought an alliance with Mexico. read more