"Exceptionalism" is not an American phenomenon. It just seems that way because America currently enjoys unipolar primacy, so it can put its ideology into action.
Most powerful nations have intentionally promulgated some form of exceptionalist ideology. Russians believe their country is exceptional because it alone can bridge the gap between Eastern mysticism and Western materialism. The Chinese believe their country is exceptional because of their civilization's unrivaled history. Brazilians believe their country is exceptional because it has blended more cultures and races than any other.
The examples go on and on... Japan, Korea, Germany, France, Italy, India... all have well publicized beliefs that some factor elevates their country above its peers. Given the ubiquity of this belief, I suspect that it has adaptive benefits for society, such as increasing social cohesion. (Or maybe it's just an innate human failing!)
There's a difference between a claim that a country is unique for some reason (everyone has one of these) versus thinking that this makes them superior or entitled.
American Exceptionalism even has a creation myth and a pantheon of gods. It's something else entirely.
"There's a difference between a claim that a country is unique for some reason (everyone has one of these) versus thinking that this makes them superior or entitled."
By your own definition, last century saw overt nationalistic exceptionalism in at least Japan and Germany, also with an associated creation myth and pantheon of gods. Depending on how thin you want to spread it, I think there's a good case for throwing in Italy and Turkey/Ottomans and probably all the European colonial powers.
Interestingly, could be "american exceptionalism" called an "unofficial religion" as well? lol