I'll attempt this. The United States enters World War I, but never sends ground forces to Europe. Germany may attempt to capture Paris with spring offensive but may exhaust itself in the attempt. 1918 still ends in armistice between Germany, France, and Britain. Any colonies taken by each power are returned. Germany keeps territory gained from Russia. The Kaiser may remain in power, but his authority is greatly reduced by reformed constitution maintaining him as a ceremonial leader instead. More power goes to the elected parliament.
Each of the three powers eventually sends troops to fight the Bolshevik uprising in the Soviet Union. With more support, it may tip support in favor of the White Army, but the Soviet Union still rises out of the fighting which has to be accepted by its neighbors. Germany consolidates its gains in eastern Europe by further exploiting and colonizing it. There probably ethnic tensions between slave and Germanic peoples which create rioting and violent clashes during the 1920s. Germany's economy however eventually begins to rebuild and recover. Trade between France and Britain with Germany is restored within a few years. As before the Great Depression occurs nevertheless. The economies of Europe including Germany are still demolished. The ineffectiveness of the German government to handle this situation leads to civil unrest in German areas and those annexed after World War I. The state becomes more authoritarian and cracks down. The state is not as unstable as OTL however though.
Fascist revolution takes place in Italy. Many urge the same type of movement in Germany or support communism instead and become significant political parties. War breaks, out, between, the United States, Britain, and Japan. Germany manages to remain nuetral regarding, its colonies in the Pacific. However, by the 1940s, Germany weathers the economic depression and stays intact as a nation. America becomes the world's leading economy after victory in the Pacific War. Trade with the United States brings increased economic activity in Germany.
Later in the 20th century, the colonies of Germany move towards independence, it remains itself a normal power in Europe.