>>I think Japan was on the verge of surrender anyway, just some careful wording and additional pressure from the Soviet Union's military might would have done it.
It can not be perceived as a sane argument, after Allies had to deal with Germans in Europe.
Your subjective opinion does not account losses, that US had when they were fighting against Japanese - outside of Japan - only fighting over very tiny islands. So, in the end they saved ~1 million US soldiers, because fight on mainland(also in China and Korea) was nightmare hell scenario for US.
During WW2 US gave to Soviet Union materials, newest machines and technological secrets(including technology and materials of atomic bomb, that supplemented and sped up development of Soviet Union atomic bomb project), what other allies of US did not receive. This narrative, that US was bombing Japan, to put Soviet Union in fear does not account for that Soviet Union had infiltrated US, that even US president was not working for US, but for Soviet Union. Even nowadays those US traitors, that gave away more, that what was agreed on Lend-Lease, have not been prosecuted, because their positions were top positions and their deed and betrayal of US is not common knowledge to modern Americans.
We can also look from that side, that USSR was unreliable ally(also to Third Reich, which USSR was preparing to invade, while it hoped that it was busy invading Britain) and did not want to enter war with Japanese, who at that point still controlled Manchuria, Korea and very large parts of China. They only entered war, because they realised, that they might miss out on piece of Japanese territories, because US would make their own peace and Japan would surrender wholly to US - only because of those atomic bombs.
For those that would think, that USSR was sparing their troops - it has not been concern of USSR until the day it collapsed and was not concern for Stalin, when he was postponing attack on Japan, like he was playing with Germans.
It can not be perceived as a sane argument, after Allies had to deal with Germans in Europe.