Why did the U.S. not enter the war?

One main reason that the United States took so long to enter the war was that it really wasn't clear which side we belonged on. A significant percentage of the population were first or second generation immigrants, and therefore still felt some sort of loyalty to their country of origin. So opinions on the war varied-of course those of German descent or origin were often in sympathy with Germany's plight. Those of Irish descent or origin were usually anti-British...but not necessarily pro-German. American idealism sided more with the British and French, but they had allied with the Russians. There was also a wave of pro-English feeling throughout the country at the time, and the U.S. had been producing war material for the Allies. The United States took so long to enter the war because the population was not clearly for one side or the other. The U.S. did not get involved until it was clear which side we belonged.