I've heard the nukes were more a symbol to the USSR than a military necessity. With no allies and diminished resources, could Japan have survived long under a naval and aerial blockade?
https://www.reddit.com/r/AskHistorians/comments/c7fk4d/why_not_blockade_japan_by_sea_in_wwii/
You may be interested in this previous answer I wrote to a similar question.
In essence a long blockade was the most defined plan the US had in prewar planning. But that also doesnt leave much for the Army to do, might take a long time in a nation looking towards peace, lacks the singular measure of payback some sought but could be too cruel for others, and would still have been part of any other invasion scheme. And even might be too passive based on Soviet plans as well to some.