What is one reason that the United States entered world war 2?

I really don't think that there was any other reason for the United States entering the war. The American public was against another war and didn't want to enter WW2 after WW1. But after the attack on Pearl Harbor everything changed in a day and we entered the War with the American people's blessing. 1) Japan bombed Pearl Harbor and declared war on Britain, the USA, Canada & Australia on 7/12/41. 2) Germany & Italy declared war on the USA on 11/12/41. 3) Bulgaria, Romania & Hungary declared war on the USA on 13/12/41.