> From their point of view, it probably seemed as if the US had already won and just decided to spike the football.
That wouldn't be far from the truth? If I remember, and it was reported correctly, the US govt deemed the nuclear bomb to be the lesser of two evils; the other being a long drawn out deescalation due to Japanese pride.
Yes, that's what's taught in US schools, but there's significant controversy among historians over whether the Japanese may have been about to surrender in the late summer of 1945 anyway.