reconstruction of the prewar society in Eastern Europe
I don't really understand, how the old, pre-war society in Russia (it was the same pre- and post-war, or do you mean the pre-ww1-society?) would be reconstructed if the W. Allies reached Central Europe before the soviets.
You forget the essential thing : Romania was an enemy ,as were Hungary and Bulgaria, thus they had to be occupied and indoctrinated ,if the Soviets did not do it, the West ( = the US ) would have to do it .
Oh, probably no one told Stalin, Churchill and FDR/Truman, that those were enemies previously. BOTH Romania and Bulgaria were considered late addition to their own camp, with BOTH having fought beside the soviets. Bulgaria has the distinction of being the only ex-Axis country, that has emerged with MORE territory, than it had pre-war. Even the unquestionably allied Poles and CSR had LOST territories.
For indoctrination, you don't need divisions, you only need a couple of collaborators and "advisors". I doubt, the W.Allies (US) were so pressed for personal, they couldn't send a couple of hundred people to each country.
It was totally impossible in 1945 that the heirs of Antonescu and Horthy would continue to rule Romania and Hungary,because 1945 was a year where left wingers dominated Britain, France, Belgium ,the Netherlands .And the US .!
Antonescu was a nobody in the hierarchy, the real Head of State was King Michael. In the same vein, the Head of State was the quasi-king Horthy, not one of the many Prime Ministers - and certainly not Szálasi, the leader of an unimportant little party.
BOTH countries were monarchies, and the W.Allies mostly didn't care, if a country was a monarchy or not. The Tenno wasn't touched, and neither was Victor Emmanuel III/Umberto II. Or whatever the name of Thailand's king was.
BOTH Michael I and Horthy had quite good connections to the West - strangely, from the five countries you mentioned, three were, and still are monarchies - so why on Earth would they be removed? Neither the Iron Guard, Antonescu's or Szálasi's guys (the latter were in the minority as it was) had ANY chance to come back after the defeat of their "sponsors".