The OP is - as everyone is saying - flatly wrong.
As additional proof Brazil was the “Republic of the United States of Brazil” from 1889 to 1930 and everybody called the country Brazil and its inhabitants Brazilians.
Mexico is offically “Estados Unidos Mexicanos” or United Mexican States. Everybody calls it Mexico and its inhabitants Mexicans.
We are the United States of America. We can call the country the US, the USA, or America, but its inhabitants are always properly called Americans.
We’ve done this before.
Since when and why is the United States called “America”
Are we the only United States?
I see the OP is not from the US, but this isn’t a case of American chauvinism, but of how language works.