I refer to the country south of me as "the US" or "the USA". To me as a Canadian I live in the Americas so I could be an American. Growing up nobody I knew called the US "America" you'd even hear "the Boston States", I have no clue how that originated.
But I've noticed over the past decade or two it's become more common for people in the US to refer to their country as America. I know it's a shortened form but still, to me, it's weird because:
Europe, Europeans Africa, Africans Asia, Asians Americas, ? (demonym for people of the entire region?)
I know some people counter with it's "North America dummy!" but wouldn't that mean the USA should be the USNA?