Speaking as a person confident that I could point out Argentina on a map, why is geographic trivia a very important topic? I'd rather have a population with a good understanding of means and medians, thermodynamics, and the relationship between rates and accumulations, than one that can readily tell me the year that William the Conqueror invaded England.
I agree but the point is that knowledge of the countries of the world is the most basic sign of education besides reading. The average 18 year old knows even less about science than geography. But geography is important because not knowing it is extremely embarrassing.
Knowledge about other countries is useful, geography less so. It would be just as embarrassing to have a conversation with an Argentinian and say "so what's it like living near Chile?"
Because literacy and numeracy are necessary but not sufficient for an educated polity. A good understanding of society, of history, of philosophy, and more all factor in. As do good critical thinking skills.
...and before widespread public education, many of them couldn't even read.