Perhaps you should read “Guns, Germs and Steel”, by Jared Diamond. It might give you some answers.
Let’s not jump to conclusions about history teachers’ responsibility for this. There are a whole lot of Americans who are strongly predisposed to deliberately reject or ignore history education if isn’t all about how great white people are.
I did not blame any teachers. There probably are lazy or biased teachers, but a bigger problem would be text books that try to serve up tepid pap instead of solid information and school boards, (themselves uneducated citizens who do not realize their own ignorance), who set low bar goals that administrations follow on a “go along to get along” policy rather than seeking to provide actual education.