Have you any idea how tired the average person especially in the Great Lakes area was getting of the war. Its all a matter of Will and frankly the desire to drive brutal invaders from hearth and home tends to trump the fervor of conscripts for a political abstraction.
Were the assumption to be made that Japan rather than receding into isolation were instead to continue the rapid embrace of European technology along with the churning of the social order that tech would bring........THEN yes Japan was quite capable of oversea expansion though the Philippines ...
A Win- being defined as the Federals going away and leaving the South alone was a possibility until the very end when Lee ordered the forces to lay their weapons down. Even defeated as a regular army the troops of the Confederacy could have put up a guerilla war of ambush, sniping and terrorism...
FDR would have found a way to start a war and blame Japan for it no matter what so that he could also join the brits in Europe- something most Americans had no desire to do.
This one requires a butterfly the size of a 747. Romans were a very conservative folk. Literally who needs power tools when slaves are cheap was the mindset.