Should American Taxpayer Dollars Continue to Protect Japan or Should Japan Build Up Their Own Military?

When their constitution was written, by Gen. Douglas MacArthur, at the end of WW2, the idea was to keep their military small in order to avoid a repeat of what had just happened. If they had a small, limited, self-defense oriented military, they couldn't entertain ambitions of a "Greater East Asia Co-Prosperity Sphere" like they had in the 1930s. But, by limiting their military to self-defense actions, they were vulnerable to outside aggression, so we took responsibility for their defense (since we were primarily responsible for destroying their ability to defend themselves). I don't think, nowadays, there would be any danger of Japan suddenly conquering all of Asia. So, it might be beneficial to allow them to take care of their own military needs and save our money for other things.