Initially drawing on an oft-repeated POD, this timeline relies on the US not being able to develop the atomic bomb in time for OTL use in WWII. The reasons are immaterial for this discussion, as far as I'm concerned.
Many people seem to think that the only logical step if this had happened would be the invasion of of Japan. This would have caused hundreds of problems, many of which we are all familiar with. However, WI the American leadership had decided to crush Japan in another fashion? Namely, the continuation of the blockade of the Japanese Home Islands (JHI) and the firebombing of Japanese cities.
IIRC, the USAAF notably firebombed Tokyo and Kobe. In Tokyo, perhaps more than 100,000 people were killed, while in Kobe 8,840 people were killed and 650,000 were left homeless. In OTL only 1000 B-29s were placed into service, but by the end of OTL hostilities over 3700 had been produced, a force that would have greatly increased the effectiveness of the American attacks.
Perhaps I underestimate the will of the Japanese government and populace, but I can't see any state surviving repeated attacks of that nature while being under a complete and total naval blockade. What would be the resiliency of the Japanese if they were bombed in some way, shape, or form almost nightly and they were under the quickly growing specter of famine? How would any peace agreement look if made under these circumstances--would the Japanese still plead unconditional surrender, or perhaps the US would have allowed Japan to surrender while keeping Hirohito as Emperor, which was in fact an American concession in OTL?