By the way, FDR screwed use over the U.S. by putting that all on us. (And a little bit on Britain) The other Allies farmed out all the heavy lifting of the Pacific War to the U.S., while expecting the U.S. to bail them out in Europe.
And you are missing a HUGE point. First of all, Russia or no, the U.S. had to put that effort in. Most importantly, if all those things you mention hadn't happened, Japan would have been an Iron Curtain country. Not an ally of the U.S.
The Soviets were blue on black, a piss into a wave.
What the US did is what drove the Japanese to surrender all by itself. The fact that another nation might wipe them out was at that point immaterial.
Blue on black.