Some Canadians and more Latin Americans are understandably irritated when US citizens refer to themselves simply as “Americans.” Canadians (and only Canadians) use the term “North American” to include themselves in a two-member group with their neighbor to the south, though geographers usually include Mexico in North America. When addressing an international audience composed largely of people from the Americas, it is wise to consider their sensitivities.
However, it is pointless to try to ban this usage in all contexts. Outside of the Americas, “American” is universally understood to refer to things relating to the US. There is no good substitute. Brazilians, Argentineans, and Canadians all have unique terms to refer to themselves. None of them refer routinely to themselves as “Americans” outside of contexts like the “Organization of American States.” Frank Lloyd Wright promoted “Usonian,” but it never caught on. For better or worse, “American” is standard English for “citizen or resident of the United States of America.”