Why was Germany unable to translate its early triumphs into final victory in 1941?

Germany was unable to translate its earlier triumphs in 1939-1941 because they over reached. Early German victories saw Germany in control of most of Europe. Instead of consolidating the territories they conquered they made 2 very big strategic mistakes in 1941. The first and worst was on June 22, 1941 the Germans invaded the Soviet Union resulting in a two front war. The seciond mistake was on December 11, 1941 Germany declared war on the US.

To sum it up really shortly Germany was unable to win because American troops were really pumped and energetic to join the war and they weren't wore down like France and Britain as they have been fighting for a long time against Germany. So basically America saved them from losing WWl.