> non-USian

We prefer to be called Americans, which is also the correct demonym; it derives from United States of America, and isn't used by any other country in English. If you can call someone from South Africa a "South African" instead of an "SAian," then the same logic applies to make someone from the United States an "American."

However, Canada and Mexico are also in the North American continent, so "North American" also refers to Canadians and Mexicans, and that's specifying which part of the Americas we're talking about. The term "American" can equally apply to someone living in Brazil or Peru (or at least "South American").

To my mind, it always strikes me as hubris for the USA to pretend to be the whole American continent.