Kune ni povos has always promoted unity while fighting fragmentation. Yet despite exceptionalism's impact on unity, I was not quite aware that exceptionalism can be the norm at every level. A 1977 study already showed that 94% of college teachers in the USA thought they were better than the average. Wikipedia's article on illusory superiority has a lot more statistics and details about this phenomenon.
A highly interesting article from the BBC associates self-inflation with individualism and exaggerated self-esteem. If the BBC's description of Hokkaido is accurate, it would make sense that the USA, which was largely populated by self-confident and ambitious settlers in the recent past, would remain a very individualistic country. It would make sense that teachers from the USA would be the most prone to overconfidence, since the USA are the most affected by individualism. It would also be predictable that less diverse populations as those in Asia would diverge less in the way each individual defines Right and Wrong. And indeed, the same article claims that self-inflation is almost completely absent from collectivist societies in Eastern Asia.
But exceptionalism is far from being limited to the individual. Some collective forms of exceptionalism will pit a continent against another, a country against its neighbors, a province against a neighbouring province, and even a city against another city a few hundreds of kilometers away. And let's not forget linguistic exceptionalism, racial exceptionalism, male chauvinism, nor human exceptionalism. If individualism increases individual exceptionalism, it might seem logical that it also favors state exceptionalism. If so, USA exceptionalism should be no surprise. Yet, exceptionalism can also be found in Eastern Asia, no further than in China.
At this time of increasing international tensions, it would help to know what exacerbates collective illusory superiority and what avoids it. Indeed, if a country managed to heal from exceptionalism, I would suggest it to modestly offer the planet its secret cure, hoping to end an exceptionally dangerous pandemic.