I think America's biggest error in WWII was the disclosure of nuclear weapons existence. If America was able to keep that secret, it would have had the one and only card in its sleeve that could've stalled USSR's tank armies in Europe.
Remember guys, the nucler detente in Europe was not something given until eighties, and would've somebody more ambitious came to USSR's political arena instead of Brezhnev, even that would be under question.
WWIII in Europe was barely avoided twice with Stalin's unexpected death, and Khrushev's "retirement." That gave NATO 20+ years to prop up defences.