You have to look at these things in the context of the war that had been going on for years at the time. Imperial Japan had attacked, invaded, and occupied any

You have to look at these things in the context of the war that had been going on for years at the time. Imperial Japan had attacked, invaded, and occupied any neighbors who had resources they might need or who otherwise might oppose them. That occupation often came with brutality and oppression at a scale that would make the Nazis blush. When the US entered the war, one of their first moves was unrestricted submarine warfare, meaning any Japanese ship is sunk on sight, regardless of who or what is onboard or where it is heading. It continued with sinking many naval fleets, re-invading many islands, generally resulting in the death of basically everyone in the Japanese garrison, as it was part of their code to kill themselves or carry out suicide attacks rather than surrender. Continuing on, we have the unrestricted aerial bombing of basically every city in Japan. The only reason Hiroshima and Nagasaki were relatively untouched so late in the war was that they were exempted from conventional bombing for the purpose of evaluating the effectiveness of the atomic bombs when they were ready. Many of the conventional bombing raids caused greater death and destruction than the atomic bombings. In light of all of this, suggesting a demonstration of the bomb seems kinda pointless. The Imperial Japanese administration would probably interpret such an act as saying that America didn't have the courage to carry out major attacks, thus encouraging them to hold out longer and requiring more destruction in the end to force a surrender. The bombings were terrible, but the real suffering was the war itself, and the only way to stop it was to force the surrender of Imperial Japan as quickly as possible. Against such an enemy, the best way to end the war with as much of Japanese society as possible still intact was to demonstrate total ruthlessness in doing anything in our power to destroy Japanese infrastructure and kill Japanese citizens as quickly as possible.