Of course the US entered WW I. The official reasons had to do with the German decision to continue unrestricted submarine warfare, specifically firing on ships of neutral nations in international waters, even passenger boats, that might be carrying goods to the enemies of Germany. The US maintained that it had the right to free navigation and neutrality. The Zimmerman note, a message from the German government to the government of Mexico which the US intercepted, asking Mexico to declare war on the US, was also cited as a reason.. . The US also wanted to bring about an end to the German dictatorship and restore democracy, and of course, the US had a great economic interest in securing our right to trade with Britain and other allied countries. . . In other words, pretty typical reasons for going to war: intelligence intercepts indicating a hostile intention of an adversary, threats to economic security, a people oppressed by a dictatorial government. . . Source(s):. Here is President Wilson's "War Speech" laying out the official reasons.:. Al doilea link e cu sursa. poti sa mai adaugi si de acolo informatii..