Japanese companies did not do very well over the last 20 years (by pretty much any metric) so objectively US executives as a group did significantly better than Japanese executives as a group. In addition you can't talk only CEO salaries without mentioning that salaries in US are overall much higher than in Japan. 13M salary for somebody managing 305k employees sounds very reasonable when senior manager/director (manages 50 people) at tech company makes 1M+.