I don’t understand your explanation Milum. Even if we do not dispute the U.S. “being the flagship of Western Culture”, how would that have translated into USians being called “Americans” by Europeans. How is this a time-saver? There is no link between the two terms.

I’m thinking US folks started calling themselves Americans because it is easier to say than United Statesians, or USians. Humans tend to take the easy route if possible, even in language. Also, since “America” is an integral part of the country’s name, I think USians appropriated the name of the continent to describe themselves.