Background: Pearl Harbor happens 18 months later than planned, and the Americans join the war effort too late to help the British substantially in an invasion of Europe. The Soviets have push to Berlin on their own and as a result, negotiate the terms of German and Italian surrender with very little other Allied influence. Furthermore, the development of the atom bomb fails and the Americans resort to an invasion of the central Japanese Empire with the help of the Soviet Kamchatka forces invading Manchuria and Hokkaido. Also, the Spanish Civil War went for the Republicans in 1938 after a botched invasion of Catalonia by the Francoists was repelled by Soviet and international units.
From West to East:
The Portuguese overthrow the Estado Novo in 1939 after the Spanish Civil war goes for the Republicans. The nation is officially named the “Portuguese Socialist Republic of the Carnation” the namesake being the revolutionary movement. (This was the name of the 1979 socialist revolution)
The IRA’s socialist groups gain control of the organization and annex Ulster in 1940, and then proclaim neutrality in the war. They create the Irish Workers’ State. The British are so concerned with the threat of Nazi Germany that they allow a peace agreement.
In 1949, many Britons are so humiliated with the loss of Northern Ireland and the Soviet occupation of Europe, as well as the loss of India and other colonies, that serious sectarianism rises in Scotland and Wales. The Soviets secretly fund Plaid Cymru and the SNP, and in 1950 the separatist parties secure independence. The Americans are so occupied with a drawn-out war in the Pacific (without the development of the atomic bomb, a land invasion of Japan was necessary) that they are unable to lend support to the British.
The French communist partisans are given control of the French Socialist Republic and a substantial chunk of Western Germany.
All former Nazi territory is under some form of administration by the Soviets, including Norway. A socialist puppet government is proclaimed similar to that of Hungary or Bulgaria.
The Netherlands are made into a puppet state of the Dutch People’s Republic. (similar to Norway) They are given some lands of Western Germany.
Germany is drawn up to be completely unable to ever unite again. Any remnants of the Bavarian Communist movement of late 1919 are put in power of the newly formed Bavarian Soviet Republic. The city of Hamburg is annexed into the Soviet Union to give the USSR access to the Atlantic, similar to Kaliningrad. The remainder of Germany is split between the German Democratic Republic (i.e. East Germany but all of the North) and the Soviet Polish Authority, which administers Berlin as an insult to the Germans. Austria has more heavy communist involvement like its neighbors. The Danes are given an obscene amount of Northern Germany, (similar to Poland receiving most of Eastern Prussia after WWII in reality) where the German speakers eventually migrate south into the German Democratic Republic.
Most of Northern Italy‘s sectarian movements are given socialist client states: Piedmont, Lombardy, and Veneto. Veneto (particularly Venice) and Luxembourg are modeled after the original model of the Paris Commune. The remainder of Italy is split between the Italian Socialist Republic and the Democratic Republic of Sicily. (Remember that the Americans/ British never invaded, so Italy is punished more heavily)
A direct puppet state is installed in Yugoslavia with a Soviet minister as dictator. (This avoids Tito)
Czechoslovakia, Hungary, Bulgaria, and Romania all are administered similarly to as they were in the real aftermath of WWII.
Greece is given all of Western Anatolia and Cyprus after the communists win the Civil war in 1948. As a final insult to the Turks (remembering the Ottoman attacks on Russia in the first World War) The city of Istanbul is put under the UN Trust Territory of Constantinople, and the entirety of Turkey is given to the newly created Kurdish Workers State, which borders Arabia.
source: Reddit – user: spiscit