It does also look cool on the map.
So very true.

It will be interesting to see if the USSR can get through the war without the army and/or people rising up (especially nationalistic components eg. Ukraine, Baltic states, southern islamic nations). Stalin has lead them into a war that will kill 10 of millions, and ITTL the USSR is most diffenitly the aggressor.
Well, I think that after the first significant *Allied advances in Soviet territories, widespread anti-Soviet rebellions from the non-Russian nationalities, like the Baltics, the Ukrainians, and maybe even the Central Asian Islamics, are to be expected, since ITTL the fascist Euro armies shall behave much more gentlemanly towards them than OTL (both because racist fanatics like Hitler and Himmler are no more in charge and because alliance with the USA reins their current rulers in) and the candy-throwing US troops shall be a singificant part of the Allied invasion forces, so they shall see advancing US-Euro troops as their eagerly-welcomed chance out of Stalinist nightmare like OTL, but with no disillusionement.
Moreover, most of the lands occupied by Soviets are to be expected to develop a strong anti-Soviet insurgency once populations taste Stalinist brutality. This is surely true about places like Finland, Romania, Turkey, Persia, and even in places like Greece which OTL had strong Communist and anti-Communist components alike in their insurgency, the latter component is to be greately strenghtened by Soviets being the occupiers. The Arabs initially welcomed the Soviets as anticolonial liberators, but I would expect them too to turn antagonistic after 1-2 years of brutal Stalinist rule. Perhaps places like Bulgaria and Serbia are going to be the ones where the Soviets experiences less insurgency grief due to the philo-Russian sentiments of the population.
The Russian people themselves are going to be a more complex case. While it is sure that many of them shall fight the war with much less determination than OTL, since ITTL Soviet Russia was the unquestioned aggressor, it is also quite possible that like OTL Nazi Germany, apolitical "Rodina" nationalism keeps them loyal to the state, at least until the *Allies make sure that they offer a clear and decent chance of survival to the Russian nation.
The *Allies shall surely make it clear they give no quarter and ask nothing less than unconditional surrender as long as Stalin and the Soviet regime remain in charge, but it is also quite possible they make a public offer of a compromise peace to a non-Soviet Russia, unlike OTL. However, the terms of such a peace offer are not going to be too generous to Russian nationalist feelings: non-Russian European territories would be lost, quite possibly also Central Asia and/or Outer Manchuria, Soviet leaders and Russian war criminals would be asked for international trials, Russian disarmament would be enforced. The *Allies could however give guarantees of territorial integrity for Russia proper, and lack of extensive *Allied occupation beyond what would be necessary to enforce Decommunization and disarmament. They could also set up a non-Communist Russian government in exile.
I think that faced with this kind of peace, some patriotic Russians would cling with the Soviets to the bitter end, others would realize that it is the only way to save Russia from total defeat, and try to rebel against Soviet rule. In a totalitarian state during wartime, beyond passive resistance, sabotage, and rebellion once the enemy forces close in, the only component able to overthrow the regime is the army.
The Russian officer corps are sure to realize after a while that the war is surely lost and Stalin shall drag Russia into total destruction, so they would likely try to overthrow Soviet rule and negotiate a peace sooner or later. Now, the rebelliousness of Russian officer corps was surely curbed more strongly than German one by the 1930s purges and the Soviet regime kept more of a strict rein on the Army than the Nazi one, so finding the guts and the opportunity for a coup is going to be more difficult for the Red Army than for the Heer.
The historical evidence of totalitarian regimes in general and Communist ones specifically indicates that coups may happen, but typically only when the regime is in disarray from impending military defeat or severe internal power struggles in the ruling elite, and their success rate is not that much good (Italy 1943, USSR 1964 vs. Germany 1938 and 1943-44, USSR 1991, China 1971). So I would conclude that as it becomes more and more clear that the war is lost, some coup attempts, from the Red Army with possible support from party moderates, are very likely to happen, but their success is far from guaranteed. There is ample justification both for Stalin and his cronies getting a bullet in the head when *Allied tanks get close to Moscow (or *Allied nukes level a couple Russian cities), as for them remaining in charge up to the bitter end in a bunker in Sverdlovsk or Samara.