OK sure that might be an exception, not least because the Nazis were, like... Nazis. [EDIT: The "might" is intentional. If USA had stayed home, the war might have ended in 1943. Isn't it possible that fewer people would have died in a much shorter war?] If you don't like Nazis, however, I don't think you can support Wilson's lying our way into WWI. That certainly cost lives, and by forcing Germany into an untenable position it created the Nazis, the Holocaust, the horrific casualties suffered by the Soviets, etc. None of those things were actually prevented by our entering WWII, either.