You're pointing out a bunch of errors, but it's not clear to me that they're schoolboy errors (i.e. errors a schoolboy wouldn't have made). I would also venture to guess that the average educated person would make much more egregious mistakes.
If this is the case, IMO it's more a reflection of the awfulness of the schooling in our time than anything else. No schoolboy in the US of a century ago would have made such egregious historical errors, because they would have been taught some actual history instead of what students in the US today get taught.
Can you provably demonstrate that education quality was better a century ago? I'm not outright trying to refute you, so much as I have a belief that people tend to overstate the "good old days", so I usually prefer more concrete data points.