Just as the western Allies figured why not let the Soviets take the hit, Stalin had nothing to lose by letting UK+ANZUS wear themselves out in the Pacific.
But once it was clear how the wind was blowing, why not jump in?
> But once it was clear how the wind was blowing, why not jump in?
The moral effect of running through the Imperial Japanese Army in Manchuria "like crap through a goose" might have been decisive in allowing the surrender to proceed, in suppressing the IJA leadership. Heck, their predictions about how they'd stop or even bleed us in Kyushuu, where they had a massive superiority in numbers and stopping was very much in the cards, looked very different in the light of the 2nd bombing, which showed the first wasn't a one off, and how they were being owned by the Red Army (not that that should have been a surprise after 1939).
> but in physical terms utterly irrelevant to actually ending the war
It was also mentioned, by the way, and now in response to what you said, that Russia acted according to agreements they had with the USA. So seeing some of the arguments here, no matter what they would have done, somebody would always paint their actions negatively. I'm only talking about this entry into the war in the Far East.
The other way, of course, would be the Japanese scheme to make us tire of cost in blood, and their Air Force and Navy had a truly unpleasant surprise in store for the US Navy with vastly more kamikazes ready than we thought, which would have been much more effective than in Okinawa due to the vastly shorter distances and navigational skills required. That was, BTW, the bloodiest US Navy battle in history.
So underestimated that half our carrier air assets were assigned to the north of the relevant area, and the planned CAPs were way to thin to have stopped all that many of them. Although we could have at least somewhat corrected those in a few days after the magnitude of the kamikaze threat materialized, but there's no guarantee of success on our part, and if the Japanese had managed, as they planned, to take out troop transports....
On the other hand, we were really angry by then, and fighting to win. Is there any indication that they thought the outcome in the Pacific was in doubt? (Serious question, I don't know.)
I don't think that means what you think it means. Unless you are comparing the defeat of Germany (as in Debellatio https://en.wikipedia.org/wiki/Debellatio) and that of Imperial Japan which was a conditional surrender - maybe a typo on your part though, in which case, sorry.
US was not put in shitty position by soviets. US wanted soviets open war on east, and the soviets agreed that they will, within 3 months, once war with Germany is over. Looking at the timelines it appears to me soviets only kept their word they gave to americans at the Yalta conference
The US was put in a shitty position by the opportunistic Soviet intervention. So we ended up with a curbed emperor, an American who fancied himself an emperor, and whitewash.
Remember that the Republic of China was still a thing, and the political implications of taking a relative soft approach to Japanese atrocities in China would have pretty severe blowback.