IIRC I pitched an idea somewhat along these lines
Not to be a party-pooper- but this is near-ASB b/c:
* Stalin wanted NOBODY skeptical from the West to see how the Soviet Union really worked. They got paraded through Potemkin villages by NKVD-vetted handlers. He had no interest in doing so for a huge mob of American, British, or Allied soldiers in his rear.
* Stalin also wanted Communism to defeat the fascists as much due to the Red Army as possible and share NONE of the credit with anyone else.
* Stalin wanted supplies, not more mouths to feed, arm, and deal with. He had plenty of manpower. As long as Lend-Lease freed Gosplan to make more tanks and ammo instead of boots, food, and clothing-
Now what could make that possible?
A coup where Molotov, Beria, or some other "pragmatist" manages to give Comrade Stalin a "dignified retirement" with a 7.62 Tokarev in 1941 and allows Western troops to help push Army Group South out of the Caucasus, especially if North Africa gets wrapped up earlier by the Brits late 1942 and can send 8th Army and what would have been the American troops in Torch through Iran to train in the USSR. This is based on the Allies getting Japanese-lucky
It would be interesting if US or RAF a/c could be based in Murmansk and help lift the siege in Leningrad. Same for US/UK/Allied fighters for CAS and air-superiority missions which would have had all kinds of butterflies as the LW has to deal with much more long-range opponents in force along the battlefront putting massive pressure on German supply lines, assembly points, and mobile reserves.
Imagine Stavka having Mossies and other Western recon assets and ability to pinpont and shred the Germans' ability to reinforce whole sectors?
Bagration happens eighteen months earlier?



As to the logistical nightmare of getting enough Western ground troops (I'm figuring 20-25 divisions) being a decisive factor in that giants' dance of the Eastern Front, I'm a little skeptical.
Getting enough troops and their gear in theater through Iran to then get on transports across the Caspian Sea and assemble to be a major pain in the ass for the Soviet front commanders to deal with
OR into Vladisvostok and shipped along the Trans-Siberian RR;
AND/OR making a number of landings of troops and vehicles in Murmansk and Archangel to lift the siege in Leningrad and push south on the Byelorussian front would be tasty.
However, I have to wonder WI D-day was in Odessa in combination with Operation Uranus and how quickly they could have rolled up the Wehrmacht if it were successful?





The difference in post-war relations between the US and USSR would be worlds apart from OTL.