In OTL, the two 1939 Polish Mutual Defence Pacts provided for English and French military assistance in the event Poland were attacked by "a European power". However, a secret protocol indicated that this expression was to be understood as meaning "Germany" (so, the UK was not bound to do anything if the USSR attacked).
WI there was no such protocol. Would the UK and France have declared war to the USSR? We would end up having a very different WWII from the beginning.
Would the WAllies be able to resist to the combined pressure of Nazi Germany and USSR?
Would the Soviets do more than their role of supplying the Reich in OTL? (Red Army units in Western Europe??? Would be awesome -though not for the population)
What would be the fate of Finland? Will Hitler help Stalin during the Winter War? Will
the WAllies intervene? (IOTL the were some plans about that)
Will Mussolini be willing to
support a communist power while he has no interest whatsoever in doing so?
Is Hitler still going to stab Stalin in the back? I know IOTL he was obsessed with invading the USSR, but perhaps when he finds himself embarked together with him and sees the usefulness of the Red Army, he might decide to postpone invasion until "Final Victory is achieved" (i.e. never)...
And finally, the most daring question: assuming greater Soviet involvement, is the Forbidden-Sea-Mammal now within reach of the Germano-Soviet alliance? (I know I'm putting myself at risk of being ASB-you-moron-ed to death here

)
OK, I've written enough. Your turn now

Comments? Remarks? Corrections? Ideas? Insults?