In fact, they were sure in charge of most of the Pacific for some time until we kicked them off the islands ... the islands we gave back! I agree that it could have prolonged things because we would have had to regroup and launch our effort w/o bases in the Pacific and Aleutians. But, it would have increased anxiety and drive in continental US. The Japanese would not have invaded US mainland (in fact, they were not prepared to do so), they knew/admitted that there was a rifle/shotgun behind every schrub ... and THAT generation was not afraid of the shadows).
Plus, in those days we had a Democratic president with guts. Harry S would have hesitated even less to use tyhe bomb(sssssssss).
Maybe the Japanese should have 'won' in the Pacific for a while longer???
PS: Been to Hawaii of late?? If so, in your opinion who runs it?? There is winning/losing, and there is losing/winning!!
Next question: What if we have left France as part of Germany??? Can we still do that????