Why did the United States become involved in World War I? Question 1 options: The United States entered the war because of an unprovoked attack on a naval base in a United States territory. The Zimmermann telegram proposed a military alliance between Germany and Mexico against the United States. American citizens in France were captured and held by Germany in return for a pledge of neutrality by the United States. The United States was required to enter the war as part of a provision contained within the charter document of the League of Nations.