A sense of separateness is not easy to measure. Most people have no idea how their own feelings would compare with those of other peoples. Nationalism runs rampant throughout the world. Unconscious racial and cultural arrogance and disdain for others is pronounced in many nations around the world. But I think the Japanese sense of distinctiveness -- is itself very distinctive.
The strength of the Japanese feeling of separateness becomes more clear-cut when one considers Japanese attitudes toward other peoples. Japanese seem to have a sharp awareness at all times of themselves as being "Japanese" and of others as being first of all "not Japanese."
Again such attitudes are hard to measure, but I believe the Japanese seem to feel them more strongly than do other peoples -- except for persecuted minorities or simple tribal peoples. The first answer of a Japanese to the question "Who are you?" is likely to be "A Japanese."
Any person who goes abroad is probably surprised at the strength of his or her own nationalistic feelings, but most Japanese are less able than most others to lose consciousness of their national origins even momentarily and are more likely to see themselves always, not just as representing themselves, but as someone being exemplars of the whole Japanese nation. A Japanese who distinguishes himself in the world is much less likely to think of himself or be thought of by his friends, acquaintances and fellow citizens as "little Ichiro" who made good, but as a "Japanese" who became famous.
The uncanny inability of the Japanese to place themselves in a foreigner's shoes is very strange. I have had a weird experience with a Japanese tourist in Canada (my home country), one which stands out in memory. About 8 years ago, I was in Vancouver visiting my old friends who, when seeing some Japanese tourists nearby, asked me to exhibit my newly acquired language ability and speak in Japanese. I soon chose a Japanese man and his high school-aged son, and approached them with a typical tourist question: "Can you recommend some good restaurants around here?"
The father looked at me caustically, perhaps shocked that I could speak "his language," then replied that he could not recommend any since he, too, was a "stranger" there.
"Stranger?" I said. "You mean you're a 'gaijin' (foreigner) here."
"No," he emphatically replied. "I am Japanese, not a 'gaijin' (foreigner). You are the one is a 'gaijin' (foreigner)."
However, unable to understand the fantastically ludicrous nuance of this dialogue, my friends were duly impressed that I had merited such an emotional response.
Ishihara, Koizumi, Abe, Aso, and most other Japanese I might venture to say, might have responded in the same way as the man did. Not until the Japanese can see themselves as "gaijin" (foreigners) in distant lands, as we all are, will their everwhelming desire to be internationalized be realized.