Answer the question of how they didn't happen, and you'll have many of your answers.Imagine a timeline where in someway the Great Depression World War II never happened.
Now,
how would been the United States in 30s and 40s,in a world like this?
Maybe James Cox President in 1920 and reelect in 1924?If you've ever seen "Sky Captain and the World of Tomorrow", it could look like that minus giant robots and evil scientists.
To stop the Depression, you'll need a government that supports keeping an eye on the market, government aid and intervention (notably concerning farmers who felt the effects of a depression before the people even thought there was a depression) and regulation rather than the feel good laissez-faire of the 20's Republican dynasty of Harding, Coolidge and Hoover.