Common knowledge tells us that the red army during WW2 was an unstoppable tidal wave of tanks and hard bitten Siberian infantry from 1942 onwards, and the Germans were fools for even starting to fight them. At the same time, as I've read into the subject, I've seen increasing historiographies suggest that the 6 million soviet soldiers on the Eastern front were close to the last manpower the Soviet Union had, and that the Soviets were almost as spent as the Germans.
Which is true?
Those same historiographies also suggest that the 4 million men of the US and French armies (less so the British after 6 years of fighting) were fairly fresh, and their countries had resources to spare after the war, suggesting that had it come down to East vs West in the late 40s, the Russians would not have had a long term advantage in troop numbers.
This is going to be a contentious subject.
The closest the Germans ever got to breaking the USSR was in 1942, by 1945 as tired and over mobilized as the USSR was the Germans were far more so, and getting weaker by the day in every way. Once the Soviets stabilized their front in late 1941/early 1942 the Germans had no chance of breaking them.
In 1942 the USSR was pushed to the brink. Mark Harrison in "The USSR and Total War: Why Didn’t the Soviet Economy Collapse in 1942?" explains how Germany was depending their invasion rapidly causing a 1917 like collapse of the Soviet economy and government, and he believes the Germans got very close, though it is impossible to say how close. He also believes Lend Lease aid at this time, which made up 5% of soviet GNP in 1942, provided a significant stabilizing effect on their economy. These were by far the darkest days for the USSR, with Germans in the Moscow suburbs and the vast majority of their industries in the process of being evacuated and set back up in the East. However, once the USSR held, and did not break, it was game over for the Germans.
By 1945 the USSR was a very powerful, mechanized, force with strong war industry, but they also were vastly over mobilized had more men then they should have in their military. This over mobilization is partly why the USSR was suffering food shortages in 1945 and then later suffered famine in 1946-1947, though other factors contributed to these famines as well, a scenario of a new war with the west around this time would have not helped their situation.
I don't know how fresh I would say French troops and manpower were, considering they just spent the last 4 years occupied and with a war going on across their country, but the US was not nearly as war weary or spent as the Soviet Union and UK was, either from a manpower or an economic standpoint. By 1945 the US Army stood at 8 million men, with another 4 million in the Navy, Maines, and Coast Guard, and growing. Between 1941 and 1946 the US population had grown by 8 million people, from 133.40 million to 141.49. Compare that to the USSR, who's population shrunk by 25 Million, from 195.4 million to 170.5 million, due to the war.
US industry, was just warmed up and producing incredible amounts of equipment and material, more than enough to supply themselves and to fill in the needs of their allies where required.