How was the return home of US WWI soldiers different than that of US WWII soldiers? The latter gets described as transformative but I've never heard much about the former. If you think that the Great Depression started in the early 20s, would you say that the two are related?

The return of American soldiers after WWII to such as the GI Bill and other continuations of New Deal policy was influenced, of course, by the fact that the New Deal had been implemented before the war, as part of Roosevelt's efforts to get the United States out of the Great Depression. Although some of the progressive policies pursued by Theodore Roosevelt, Woodrow Wilson, and others before and during WWI were continued after WWI ended, the agenda of the Harding and Coolidge administrations was very much a 'return to normalcy', entailing a more conservative economic/domestic agenda. 1920s American isn't exactly my area of expertise, so if any users more knowledgeable would be able to add, it would help!

For returning African-American soldiers, the life they experienced in France and the values for which they had fought, democracy and national self-determination, ad an important impact, returning as many did to a revived KKK and horrific race riots. In many ways, these soldiers galvanized African-American civil rights efforts, with wider implications for the later movement in the 50s and 60s. The recent book Torchbearers of Democracy is an excellent source for this.

American arrivals in France as part of the AEF also had an impact on the American Emigree community in Europe in general, in France in particular. Many writers especially, taking to the modernist themes that had appeared well before the war, became part of what Gertrude Stein called 'the Lost Generation', a term that did not solely denote disillusioned WWI vets, and which her friend Ernest Hemingway seems to have taken issue with.