My two-cents; one scenario out of many plausible/possible ...
The British & Canadians are out of manpower. The US is stretched and is on the wrong-side of re-orienting itself for downsizing & redeployment to the Pacific.
So, things go very badly.
However, as some have suggested, there are a lot of countries/people who are very tired of being overrun and the partisan/guerilla resistance builds & builds, fueled by Russian atrocities ... Despite intense efforts to suppress same, these activites have an impact on the Russian forces and their advance ... German forces re-arm themselves, oft-times with assistance of local Allied Commanders .... Many die gallantly, but die they do -- no miracles of Tigers & Me262's & all that -- but the impact on the Russians is significant nonetheless ...
Following the initial shock, the Allies bring to bear the one thing they have -- strategic and tactical airpower. Despite the size, and even quality, of the Russian air force, the Allies have had several years to fine tune their methodology and have some pretty good numbers of their own ... Of course the assumption has to be that the Supreme Commander can prevent the air force(s) from conducting a purely strategic campaign and can focus their efforts on round the clock carpet bombing of advancing forces initially, then moving back to the Army level Command-and-control & logistics chains, then back to Front level. Russia was too vast & too dispersed to think of a true strategic campaign against strategic resources and manufacturing until much-much later ...
The Pacific War is continued, as is, without any massive build-up for the invasion of Japan. Island hopping continues to shrink the Japanese sphere of influence until basically the home islands are isolated. Efforts continue in China. Some airpower is diverted back to Europe or to strike Russia from the east or south. A couple carrier task forces prowl Kamchatka and onwards.
Before the end of 1945, the Russian forces are halted along the Rhine river and a line pointing roughly southeast toward the Swiss-Austria border.
No German technology is cloned -- there isn't time. Luftwaffe'46 doesn't happen.
Nukes are not used, at least not in western Europe. They haven't been tested at the time and when faced with the decision the thought of employing them against their own lands and countrymen and the continent is too much to bear. There are not enough of them to make a difference anyway.
A couple nukes are eventually used against Japan, and a couple more tossed into Russia, but not on Moscow -- racism still counts.
War-weariness on both sides turns into stalemate and for some number of decades thereafter there is little to no change in status. The Cold War happens, just differently. The results of WW2 in Europe & Asia are much different -- the number of possibilities become large & hard to predict.
-- Probably, the Allies care little for Korea and if there is ever a S.Korea, they do nothing when N.Korea invades ....
-- With all trace of the Holocaust obliterated, as well as x-million Jews, and everyone's attention focused on the stalemate, surving Jews are assimilated into what is left of Europe and never move back into the Mid-East which then is left to the various Arabic/Muslim nations ...
-- France, despite its proclivity for communism, looses its enthusiasm for Russian hordes, and the equivalent of NATO isn't tossed out -- in fact the threat is so real that DeGualle is soon tossed out of office & never heard of again ...
-- Britain resumes its' role as an "Island Fortress" and must suffer thru decades more of "American occupation", eventually loosing its identity.
I have an alternative scenario where the US just pulls out & lets Europe be overrun ... The world then divides itself into roughly 6 parts -- North America (US & Canada + Europen evacuees), Central/South America (but with US holding on to the Canal), Africa/Middle-East (which becomes largely irrelevant), SE-Asia/China, Russia/Europe, the Pacific (basically aligned, in pieces, with either Asia or N.America).
John
