Just a scenario that has been playing out in my mind the past few days. What if the Soviet Union put its faith in its alliance with the United States and the principle of Collective Security rather than try and take over Eastern Europe? This would have been incompatible with paranoid personality of Stalin so the assumption is that he is out of the picture soon after V-day and a relatively more pragmatic leadership evolves around a personality like Beria, or Zhukov. This leadership honors its commitments to the alliance and does not impose Communist Governments in the Eastern countries but allows most of the existing regimes to continue after purging the fascists while simply supporting the local communist parties. A range of Governments would emerge in time of Eastern Europe; from those dominated by the left wing like in Yugoslavia to staunch anti communists in countries like Poland.

A few short term scenrio's might be; the alliance with the US would continue and there would be no NATO. There was mutual goodwill between the two countries during their common struggle against Nazism, so in the absence of a Communist takeover of Eastern Europe there is no reason why this wouldn't continue. Germany would be allowed to reunify, but would remain disarmed for much longer and probably have to pay more reparations. Given the absence of the Soviet threat, the first German election might have been won by Kurt Schumacher and the Social Democrats, instead of Konrad Adenauer, given that Eastern Germany was more likely to support the SPD in the Weimar Republic. De-Nazification would continue for a lot longer and many more Nazi criminals would be brought to justice. Left wing parties in general would be stronger across most of Europe

Colonialism might have ended even sooner, with the two superpowers united in their opposition to it. Wars might still have occurred in Korea, Vietnam and Afghanistan but might not involve major operations by the superpowers.

Overtime, some tensions and cracks would appear in the alliance given the extreme divergence between the Communist and free market world views. The centuries old Russian tradition of expansion and interference in neighboring countries would have manifested itself in different ways. After Europe recovers from the devastation of the war, it tries to re-assert its authority and influence by some form of unity between the major powers like Britain, France and Germany and pushing to the creation of the EU.

A more enlightened Soviet leadership might take steps to reform the Communist system following stagnation would probably still would have happened by the 1970's. In the absence of a costly arms race with the West, it might have succeeded into evolving into an authoritarian Corporatist state like China today and manage to preserve its unity to the current day, with secessionist movements in places like the Baltics, Western Ukraine and the Islamic republics.