From what I have read, both American and Japanese war games outcomes defined Japan’s defeat sooner rather than later.
Admiral Yamamoto did not believe Japan could defeat the U.S. and said he only believed he could mount effective offenses for six months—a prediction that proved accurate. And the Japanese Army command determined what has been stated elsewhere here, once they found out Americans owned guns—any Japanese offensive across the continent would have been a disaster because American civilians would have shot their army to pieces. Besides, not only would we have had a mounted American military presence of the Word War II army, Marines and Navy, we would have had the veteran survivors of WWI on the ground. The WWI guys were not all old men. Many or even most were middle age. In short, by the time the Japanese Imperial army got to Dallas, they would have been surrounded by hundreds of thousands of thoroughly urinated Americans. (Except I really think they would have been in real trouble by the time they got to Yuma.)
“...by the time they got to Yuma.”
Wasn’t that a Glen Campbell song? :-)