Anyway, Americans needed to show off their newly acquired nuclear capabilities. Not to Germans or to Japanese. And not to Italians. It was needed to demonstrate their superiority to Soviet Union without bombing the Soviet Union.

As someone else's here already posted out, military heads made it clear that bombing Japan was not needed for their surrender.

None else had gone that far with nuclear energy and bombs. Likely.

IMHO it was needed for something else much more political.