Participation in the World Wars. German was in the right both times. If we did anything at all, it should have been to fight alongside the germans to defeat the Russians, and to defeat the Chinese. Pretty much, the USA is always wrong. Always has been. Puritanism, social democracy, and Communism share the same origins.
https://www.quora.com/What-is-the-biggest-mistake-ever-made-by-the-American-people