If America didn't want communism so badly, why didn't they take a stand then? They took the easy option of nuking Japan.
Because it would have been too tragic. Nuking soviets wasn't an option. It would have affected the European continent, no one knew how badly, at the time, and it was too risky.
I doubt Japan would have been nuked if they would have surrendered and not been so aggressive. It was a last ditch effort to end the wars.
It's still a mystery why things went the way they did. Why did Britain and the US allow the pact between the USSR and Germany, then meet in Tehran with Stalin in 1943? That's strange. Did the soviets feel stabbed in he back, did they finally realize National Socialists were complete nutjobs?
It's easy to see why the soviets weren't challenged after the war. What is murky is why Hitler wasn't challenged before.