1917
during worl war 2
1917
1941
1914
1917
on decmber 8 1941
The US enters WW1 in 1917
1917
1909 to 1944 The US entered World War 2 in December of 1941.
Knowing which war is being asked about might help in answering the question.
It wanted to stay isolated. It did not want to get involved into a 'European' affair. The German sinking of the Lusitania was a reason the U.S. entered Worl War I and the Japanese bombing of Pearl Harbor, Hawaii was the reason the U.S. entered World War II.