without US aid assistance via lend lease, without the allied strategic bombing campaign tying up much of the luftwaffe and anti air defenses, and without the threat of invasion keeping millions of german soldiers in europe, the soviets would have been smashed before they could ever set up a counter attack. if moscow was taken, the people would give up on their communist overlords and capitulate.
You alluded to the pressure the U.S. and Britain put on Germany; and I fully agree that pressure was immense. Even in 1940–before the U.S. was technically at war–its industrial production created profound implications for the balance of power in Europe. With massive numbers of American aircraft being produced and sent to Britain, Germany had to either a) find a way to keep pace, industrially, with the U.S. and Britain combined, or b) watch its cities and people be destroyed by waves of British and American bombers. The invasion of the Soviet Union was largely precipitated by the desire to allow Germany to attain the raw materials and industrial capacity to achieve outcome A.
However, keeping pace with the production capacity of the U.S. and Britain also required Germany to invest heavily in its own production facilities. That investment diverted effort from what would have been immediately useful production against the Soviet Union. During 1942, the Soviets out-produced the Germans 3:1 or even 4:1 in all major land categories of production, and even out-produced the Germans 2:1 in planes.
Prior to launching Operation Barbarossa, the German military staff had incorrectly believed that the Soviet Army consisted of 200 divisions. Divisions which had fought very poorly in the Soviets’ 1940 invasion of Finland. In the spring of 1941, the German Army consisted of 150 divisions; 100 of which were used for the invasion of the Soviet Union. But in the months after the invasion, the Soviets were quickly able to expand the size of their army to about 600 divisions. Given the imbalance of sheer numbers, it is very unlikely Germany could have prevailed in a war against the Soviet Union even despite its military’s advantage on a man-for-man basis.