What events after World War 1 led to US entry into World War 2?

Answer 1

Pearl Harbor mostly. The Americans had adopted a policy of isolationism.

AnswerThe attack on Pearl Harbour was a majour contributing factor, yet the main reason was that it was evident that the Soviet Union would win the war in Europe, and the USA wanted to limit the resultant sphere of Soviet influence by liberating and temporarily occupying part of Europe instead of having the Soviet Union liberate all of Europe and therefore probably establish a Europe-wide sphere of communism. AnswerThe continuum of history is such that it would be difficult to list ALL the events that let the US to enter WW2. Suffice it to say that there are dozens, even hundreds, mostly minor. The big one was, of course, the Japanese attack on Pearl Harbor, but that was preceded by Hitler's decision to allow his submarines to sink American merchant ships in the Atlantic.

The previous answer, that the US entered the war in order to limit Soviet influence in Europe, is hogwash. I chose not to delete it (as it should be) in order to illustrate how certain world views can taint history.

When the US entered the war in December 1941, the Russians were busy, not dominating Europe, but finding new ways to get their butts kicked by the Germans, who were camped -- yes, in the snow -- within sight of Moscow. There was EVERY indication and expectation that the Germans would quickly and totally demolish the Soviet Union.

Worries about Soviet domination of post-war Europe were ZERO in 1941.