Is it possible for the Soviet Union to decide to invade Western Europe in some reverse Operation Unthinkable after the Second World War? They had the numerical superiority on land, and much shorter supply lines than America. The US had no more nuclear bombs left for a while, and the British, Germans and French would likely not have been able to put up much resistance in the face of the much larger Red Army. The USSR was ruined, but could they somehow decide to go to war again?
POD is flexible, but keep the timeline as close as possible to OTL.