So the US ambassador needs to conduct the obligatory “nemawashi” that makes every other US-Japan policymaker’s job easier and then get out of the way. A well-connected ambassador, particularly one with political gravitas AND a close relationship with the president (the problem with Schieffer being that he had the latter and not the former) is useful for reassuring the Japanese that the relationship is important—and that’s pretty much it.

Of the list you provided the only major exception to this mode was Mondale, who was, as Funabashi Yoichi wrote in “Alliance Adrift”, “secretary of state for Asia-Pacific affairs”; that was only because Warren Christopher was clueless about Asia, and in any event, Mondale was secondary in the process of alliance revision to Nye and other officials at the Pentagon.