>>17891913 (OP)
By 1945 the Japanese were giving bamboo spears to civilians. Every civilian with a spear is one less civilian growing rice, and their soldiers were already subsisting on maggots and grass. Most of their industries and transports was burned down.
The Americans however were well-fed, well-armed and, more importantly, their industrial base was untouched. Sure. The Japs could still kill and the kamikazes could sink a lot of ships- but the Americans could replace those losses.
And if, nothing else works. Wait for them to become bone and skin while the Russian bear starts marching down from the North starting from Hokkaido to Tokyo.