In the US teaching load is assigned in terms of courses or credit hours per year and varies heavily between "teaching schools" and research schools. For example, I currently teach undergraduates at a teaching school (i.e., it does virtually no research, but has the name university attached like most institutions) that has a load of 30 credit hours per year, and am moving to another teaching school that has a load of 33 credit hours per year.
At a research school nearby I know lecturers (no research) teach 3-3 (3 courses in the fall semester, 3 courses in the spring semester, and mostly 4 credit courses). Professors (researcher and teaching load) at the same school taught 2-2 (2 courses in fall, and 2 in spring).
A credit hour is approximately 15 lecture hours over the course of a semester, so these loads vary from 33*15=495 teaching hours per year (9.5 hours / week on a 52-week year), to 6*4*15 = 360 hours per year (6.9 hours / week on a 52-week year). For this spring semester I am currently teaching 11 hours of lecture per week and an additional 4 hours of lab sessions per week. My load is usually lighter in the summers, but not by that much.