Well... it's hard to compare, since other stats have different topics. On average, since NSW is the most consistent, and since NSW is pretty rigourous in its coverage, I'd say yes. QLD's system is interesting, but lacks consistency from school to school.
Re Americans: Just straight comparing syllabi, you'd think they're pretty equal. But talking with friends who live there and are studying things like AP calculus, for the students that WANT to excel, they excel. Generalising of course, but here, there isn't much of that until university.