I was downvoted simply for suggesting another poster who hadn't seen it before, and was it really a thing, do a search so they could see different examples it.
Other people here are downvoted simply for giving their (American) experience, that maps showed the US at the centre.
Is it supposed to be a secret or something?
It's probably something decided by state education boards, so whichever map your state decided was all you saw for twelve years. Leading you to think the entire US had the same.
As an aside, I also had 6 years of American Revolution, all told. Every time we moved, the new district would be starting that unit. So annoying
Although it can seem pettily nationalistic (and probably is to some extent), for quickly illustrating "You Are Here", and the relative positions of other countries to your own, centring maybe makes more sense than having some far away country at the centre.
It seems pretty common/natural in different countries too. I wondered if a 'most accurate map' exists, and found Authagraph:
https://ourplnt.com/wp-content/uploads/2017/06/AuthaGraph-wo...
https://ourplnt.com/authagraph-probably-the-most-accurate-wo...
It's not difficult to find the origin country of the map, Japan.