the economic downturn of the Great Depression was coupled with a very very bad drought in the Midwest where the majority of the food for the nation was grown or ranched. This decrease in supply led to the Grapes of Wrath type scenes we're all familiar with from this time period.
As for World War II, I doubt it would have happened the way it did. Germany's immense war debt from WWI directly led to the rise of the Nazi Party. For as bad as they were, the Nazi's did good for Germany and most Germans. They turned around the economic depression they were suffering from and provided food and clothing for people who didn't have it. I've even heard a seminar from a Jewish survivor of Auschwitz who specifically said, "Hitler did a lot of good for Germany and Germans." He also pointed out that it was Hitler's lieutenants who came up with the idea of mass slaughtering of human beings, not Hitler himself.
But Hitler was evil and I'll specifically go out of my way to dance and then pee on his grave if I ever get the chance to visit Germany.
