In the above mentioned numbers i have gotten these figures

the Soviets had in troops numbers.

Rifle Divisions, Total 500+, 9,700 per division
Tank/Mechanised/Motorized Division, Total 200+, 10,000 per division
Cavalry Divisions, Total 125+, 4,800 per divisions
Penal (Convict) Divisions, 120+, 9,700 per divison
Artillery Divisions, 95+, 4,300 per division

If this thread was to occur then the Western Allies would have no choice but to release all prisoners of war and re-mobilize them that takes time, But i would see that at least the U.S would also have no choice to forge an alliance with Japan and Nationalist China to go on the offensive in Eastern Soviet Union as to open up a second front.

In the end i can't see the Soviet Union lasting more than six months with all nations against it.