What are the common reasons for the initial defeats of the USSR and the USA?

In both cases, the factor of surprise and suddenness played a role. Germany attacked the Soviet Union without warning on June 22, 1941. This attack was sudden, Stalin does not believe that Hitler could strike without proper preparation. Units of the Red Army at the initial stage of the war were not ready for defense. The same situation occurred in the United States, when it was unexpectedly attacked on December 7, 1941 by a powerful grouping of the Japanese fleet. Then hundreds of aircraft from aircraft carriers took off and launched torpedo-bomb attacks on American ships of the line. All American ships were sunk or badly damaged. This blow significantly weakened American forces.