From research I've learned that placing a high value on blending in is a cultural thing. There's the resulting good, like the focus on harmony which promotes good relationships (and is a major contributor to the low crime rate), and there's the bad, like spurning those who look/speak different (I've heard stories from a few who went to visit seeing signs that gaijin aren't allowed in certain establishments, etc).

That, and things like being an enthusiastic and early customer of British industrial/steam powered equipment in what we would broadly call the Victorian era. The early Japanese pre-dreadnought and dreadnought class battleships, for instance, were a clear descendent of British (or competing French) designs. Railway stuff as well. Lots of things that weren't British origin were American.

Korean men and Japanese women make up the biggest share of international marriages in Japan so there's something more going on here that makes Japanese women highly desirable to men in general.