If the Germans could take and hold the first and last city in 1941 then Stalingrad in 1942 the USSR is effectively finished as a resisting power. They would have lost huge population, industrial, and transportation centers, as well as resource areas, plus in the case of Leningrad Murmansk would likely fall very soon after, which means a lot of LL is cut in 1941-42. I think then the Allies cut bait on LL and let the Soviets suffer their fate, hording resources for themselves. Japan probably even gets in in 1942 to secure their border with the USSR after Stalingrad falls, while Stalin probably goes into purge mode and is either removed himself or collapses the ability for the military to operate. Bad, bad news though no matter what.