In terms of "before and after, results of actions lead to consequences," here are the effects that I know of:
As for America, World War I established a base of greatness and showed the rest of the world how powerful this rather young country actually was. America went through a short term of greatness and prosperity known as the "Roaring 20's," which benefited much of America and the western world. As for Germany, Germany suffered a short period of poverty due to the massive amounts of reparations that needed to be payed to the allied countries. During this time, a hatred known as Anti Semitism was strengthened in the hearts and minds of the German people, which eventually led to the founding of Hitler's Germany.