First, to get a anti-comintern war let the Soviet Union become offensive. True, the French feared Germany more than the Soviets, but that would change imidiately if the Soviets seem to get Germany. So why not instead of introducing a right-wing conservative government in Germany introducing a Soviet Germany that wants to build up a communist union with the Soviets? In this case, the French would readily fight alongside Freikorps until Moscow, and so would the British and most people they liberate along their way.
Second, the Soviet Union would certainly loose a full scale war, even if they get Lend-and-Lease until 1945. The western Allies have a gigantic production advantage, which the Soviet Union never reached - and certainly wouldn't reach if the war goes on. Then, the western Allies can count on troops from every country they liberate. The Germans are defeated, true, but they would voluntarily fight on against the Red menace. So would hundrets of thousands of Poles, Czech, Hungarians, Bulgarians, Romanians, Ukrainians, Balts, RUSSIANS!, Japanese, Chinese, Koreans...
The advantage in numbers would soon be made up.
The Soviets would have a war on all fronts, no supplies from whereever, no nukes, inferior production, sooner or later inferior morale (after all, they lost 20 millions in fighting Germany back, now Germany comes again, but this time under the leadership of the US, Britain, France, Japan...), no nukes...