1920s America was prosperous for a few reasons. Perhaps the most important reason was that this was right on the tails of World War I. With Europe devastated, the United States was able to capitalize and become a world manufacturer. Another factor from the war was that many European countries borrowed money from the United States during the way and were slowly paying it back, making America a creditor nation. The advent of purchasing new items - in particular radios - on credit and the installation plan allowed for prosperous times. Europe did not prosper as the United States did, but rather parts of it faced hard times. Germany, in particular, was devastated due to being blamed for the war and facing heavy reparations. This was one of the causes leading to the rise of dictators, including Hitler himself. Bope this helps.