I freely admit a prejudice. It is against the concept of "national character," or kokuminsei in Japanese. Is there really such a thing or is it merely a jumble of stereotypes, whichever is the country or culture in question?
There are, most certainly, unique features characterizing the people of every nation. Some are dictated by history; others, by linguistic conventions, mannerisms, and the decorum — or lack, thereof — of socialization. But all these can change with time. After all, a Japanese national characteristic of 1810 would hardly have been immutable in 1910, and even less so in 2010.
I recall a conversation I had in the mid-1980s with a producer in the dressing room of a TV talk show I was on. We were well into the season and had had quite a few pleasant personal discussions when I realized that I hadn't asked him where his hometown in Japan was.