I wrote a reply to this topic in the facebook post and I'll gladly offer my insight here also. Bit I'm too lazy to write it all out again, so I'll offer a snippet instead. :)

So here's my thinking the Army Group South turns North (ignoring Stalingrad) and the Army Group North goes South (ignoring Leningrad) and creates a Pincer around Moscow. Trapping the capital and achieving the main objective of Operation Barbarossa and capturing Stalin and the Politburo. With the head of the snake, the whole Russian nation with all its ethnic diversity and undercurrent of dissension again the Communist party would have been ripe for the taking probably without a shot needing to be taken

Of course, what works against the Germans was space and the harshest winter approaching. Throw in an able commander in Zhukov with his reserve of Siberians equipped with material equal and if not better than the Germans then, of course. Add an overconfident Megalomanic Fuhrer without clear objectives and a German army equipped for a summer holiday on the Volga then we all know what happens next.

But back to the question what if Russia failed to stop the German offensive?

Japan would link up with Germany with the trans-Siberian railway making good use of delivering new German designs and advisors plus all the necessary resources to grow its Asian Empire

Germany would have time to build up resources and an Atlantic wall only Rommel would dream of or perhaps even then there might not need to be so defensive.

I can only see a domino effect Russia falls, Turkey Falls, Middle East, and its Oil Fields fall, Egypt and North Africa falls and so on...

This leads to the question would the Allies Nations survive or would the Robert Harris novel Fatherland be fulfilled?

Over to you...