>"Since the 1970s, all American schools have taught the metric system."

Well they've been doing a terrible job at it then, because I'm a European guy living in the US and my US friends never get a sense of what I'm talking about if I use metric units.

Additionally, I TA'd 2nd year level mechanical engineering courses at a very large state university when I was in grad school, and most of the students would get stumped on problems that involved things such as converting a result in centimeters to millimeters, etc, requiring me to explicitly write "1 cm = 10 mm" on the board/assignment papers.