[bsanr]

>In what sense is Japan "internationalist"?

Japan has scarce natural resources. It's also situated on an archipelago. Without international (and, importantly, overseas) trade, it ceases to exist as an industrial civilization. The necessity (and, yes, in contradiction with the traditionally collectivist and exclusive character of its people's culture) of international relations to the survival of the 21st century Japanese state is well-known, and the source of no small amount of consternation on the part of those concerned with the notion of a Japanese identity. I'm not educated or familiar enough with their cultural dynamics to say for certain, but I can imagine the exclusivity of Japanese identity being partially a reaction to its precariousness.