I'm just an anecdote (but: an anecdote from exactly the kind of school district you're trying to dunk on) but I checked and OPRF students do Euro history the first half of Grade 9 (in World History A), then US History, then again in Grade 11 (if they elect it).

It seems to me that none of the time students spend on subjects like Mesoamerican History are "inordinate", since students take history for a fixed, small number of semesters. You can definitely ordinate the time here.