You really don't see the difference between needing hundreds of planes operating over the course of months to inflict terrible but imprecise and spotty damage vs. a single bomber being able to wipe away factories, railyards, garrisons, etc, and disable everything nearby in a broad swathe, by simply getting through once? Really? You don't see the issue with the Japanese quite EXPLICITLY making their plans to force an American negotiated peace around inflicting unacceptable casualties and the sudden ability of the Americans to duplicate the force they previously needed to expose dozens and hundreds of fully crewed and loaded bombers over multiple days and multiple sorties, to a single heavy bomber in one pass?
I'm not sure why you're attempting to downplay the shock caused by the atomic bomb on the Japanese government. The cabinet meeting on August 7 immediately began discussions of a surrender according to the terms laid out by the Americans in the Potsdam Declaration, and ended inconclusively rather than with acceptance or rejection. The atomic bombings were psychologically devastating, and gave great weight to the faction within the Japanese government advocating the acceptance of the Potsdam Declaration. There were MULTIPLE coup attempts, even after both atomic bombs and the Soviet intervention, to attempt to stop the surrender. Do you really think that the deaths of 350,000 people and the destruction of multiple strategically vital points in the anticipated defense of the home islands, in that context, had no significant weight on their decision to surrender; that the Soviet invasion was enough and the considerable resistance to surrender would have been unchanged by the absence of the bombs? I find that very hard to believe.
The idea that neither bomb, no blockade, AND no American invasion would be needed to force a Japanese surrender is not a mainstream modern academic view. There's a reason Gar Alperovitz is not taken seriously on the subject anymore. Hasegawa's book was iconoclastic but ultimately gained little traction, not because it was necessarily poorly researched, but simply because it falls prey to the natural bias of its author to lend undue weight to the matter they specialize in (the history of Russia-Japan relations). Hasegawa's argument rests much heavier on assertion than revelation - he offers context of the diplomacy between Japan and Russia, but shows nothing new in terms of facts or connections that would warrant the extra weight he assigns the Soviet intervention, nor does it show any new evidence or connections to lessen the weight of the evidence in favor of the need of further pressure to force a Japanese surrender. (full disclosure: I only vaguely remembered the book's reputation for reaching for its conclusions beforehand; I read Hasegawa's article after your post but not the full book for... obvious reasons of time and effort). Hasegawa also makes the claim that the Japanese were surprised by the Soviet attack, which is DEEPLY questionable at best.