What event directly led the US to enter World War 2 was?

Who settled Manhattan island first? What are facts about Connecticut in the 1700s? What is the value of a 1963 US 1 dollar bill with a green seal? How much did a pick cost in 1849? What is the value of a 1789-1907 George Washington gold dollar? What states are in the Middle Atlantic region? What is the value of 1965 churchhill coin? What were the former slaves called? What is the value of a 1901 copper-nickel Indian head cent? What are important events in minnesota's history? What is the Value of a 1934 A twenty dollar bill of San Francisco with the serial number L40736387A? Who invented ironclad ships in the US Civil War? Which act passed by the British government stated the colonial assemblies could not issue money? What were the causes for the American Civil War? What kind of adjective is the word American in the follwing sentencethe soldiers saluted the American flag? What goods did the New England Colonies export to England What did they get in return? Under the National Banking Act after national banks deposited government bonds with the U.S. treasurer they could issue currency up to percent of the value of the bonds? What is in the center on the back of the US 1 dollar bill? What is a 1804 Indian head penny worth? How did American citizens help in the war effort during world war 1?

What event directly led the US to enter World War 2 was?