I doubt anyone would say that Reconstruction, and the occupation of the Confederacy by the Union Army in particular, was a ringing success. Based on that experience, you probably would have assumed in 1945 that the occupation of Germany after World War II would be a colossal failure. You would have been wrong. How do we account for the difference?
In both cases, the devastation of the occupied land was nearly total. It would seem, however, that the embittered residents of the Confederacy were more emotionally invested in their antebellum society than the Germans were in the Third Reich. In addition, the Allies felt they had carte blanche to try to remake German society, while attitudes towards the Confederates were still softened by feelings of national unity and respect for property rights and constitutional norms.