So as someone from the USA, I'm shocked by the amount of people missing the point of this.
The fact is, the USA does not exist without it's relation to it's mother continent, just like Mexico and Canada are part of N. America too.
We ARE all Americans, continentally. The point with this quiz was to get people to stop generalizing anyone not from the USA as non-Americans.
Just because this country is internationally known as America, doesn't mean we're the only country existing in the Americas. Our being "America" is just a nickname. We are officially the United States of America. "Of" in the title is referring to the continent. This was decided by the Continental Congress back in 1776 as our former name was the United Colonies.
So instead of being perplexed, offended, or just angry at the dev for opening your minds with actual facts, maybe you can use this time to expand on your knowledge and accept that on this side of the ocean, we really are all American...and highly likely mixed with Indigenous and African blood.