“American” is the official name, though throughout history attempts have been made to find alternatives. You can read more on the Wikipedia page: en.wikipedia.org/…/Demonyms_for_the_United_States

The only officially and commonly used alternative for referring to the people of the United States in English is to refer to them as citizens of that country.[18] Another alternative is US-American,[19] also spelled US American.

Several single-word English alternatives for American have been suggested over time, especially Usonian, popularized by architect Frank Lloyd Wright,[20] and the nonce term United-Statesian.[21]

Writer H. L. Mencken collected a number of proposals from between 1789 and 1939, finding terms including Columbian, Columbard, Fredonian, Frede, Unisian, United Statesian, Colonican, Appalacian, Usian, Washingtonian, Usonian, Uessian, U-S-ian, Uesican, and United Stater.[22] Names for broader categories include terms such as Western Hemispherian, New Worlder, and North Atlantican.[23][24][25]

Nevertheless, no alternative to “American” is common in English.[18]