Japan's government is nowhere near the US. For one thing the Japanese don't shoulder the responsibility of policing the world so they don't have to spend so exorbitantly on the military.
I guess comparisons can be made between Japan and the United Kingdom. Both are constitutional monarchies, both have a Parliament form of government. Both have fairly elaborate social network built into their government. Once again neither has to spend as much on the military, intelligence, and arm twisting as the US so there is more money to spread around. The Japanese are far more efficient and culturally they put far more into accomplishment than making money for the sake of making money.