Until the "joke" of the flat earth got way out of hand and you realise that the internet is great at everything aside from context and this is something that isn't taught. Although I remember a professor screwing with us and changing a proof on Wikipedia to catch people out one term...

That’s a shameful act of vandalism on the part of the professor… :(

Not sure I'd agree. It was very public, very much reverted and very much a demonstration of the context of the internet. Not to mention a very easily verifiable proof, if people picked up the textbooks and noticed the subtle mistake.

He literally defaced a public good, and this cost the intervention of more sensible adults. A small cost, but still.

> it's been decades since I saw this hung up in classroom

Try to buy a world map for a classroom. Search things like "world map for classroom", "large world map", "world map poster" in Amazon. Probably 95% of the maps returned for these search terms are Mercator, but there are a few that aren't. American elementary school teachers are generalists, they teach geography without having specialized knowledge of geography, much less map projections. If such a teacher is buying a world map for their classroom, they're very likely to pick a Mercator map simply because that's what most classroom sized maps use.

(Despite this, American children are not raised to think that Canada is powerful...)

Only if you think the history of now is moot.