Probably it would look like old style Yoshinkan with people trying to bash each other around.
Note that Funakoshi Gichin wrote in the first edition of his karate manual that karate was a good implement for 'Japanese-ifying' conquered people. This seems to have actually happened in Korea. In a series of articles in the old Dragon Arts magazine, Robert Dohrenwend has pretty cleary showed that Tae Kwon Do is simply Shotokan Karate taught to the Koreans during the Japanese occupation, and obviously Korean kumdo is just Japanese kendo. So, this is what the future would have looked like with a triumphant Japan--we would all be doing martial arts--just as we're doing now!!
Some of us make a point of avoiding the Imperialized martial arts. Bleh!