gentilicio

listen to the pronunciation of gentilicio
Spanisch - Englisch
demonym
A name for an inhabitant or native of a specific place that is derived from the name of the place

Why is it that people from the United States use American as their demonym?.

A demonym or gentilic is a word that denotes the members of a people or the inhabitants of a place. In English, the name of a people's language is often the same as this word, e.g., the "French" (language or people). Some places, particularly smaller cities and towns, may not have an established word for their residents; toponymists have a particular challenge in researching these. See also ethnonym
a name for an inhabitant of a specific place that is derived from the name of the place
A pseudonym formed of an adjective