FWIW, every non-US American I've ever known or worked with (from Brazil, Uruguay, Argentina, Chile, Ecuador, Colombia, Belize, Guatemala, Mexico, Canada) has be

FWIW, every non-US American I've ever known or worked with (from Brazil, Uruguay, Argentina, Chile, Ecuador, Colombia, Belize, Guatemala, Mexico, Canada) has been more amused than bothered when I've asked how they feel about US Americans calling themselves "American", and excluding non-US Americans. Non-US Americans don't seem to care, and they think it's silly that I'd wonder whether they did. It still feels dismissive and rude, so I try to avoid it -- but evidently it's not a significant or widespread concern among those with standing to be offended.