You can't make this stuff up.
Personally, I got a kick out of the midwesterners who used to use the metric highway signs for target practice.
They'd have a blast outside the country. I did an AT in the Netherlands with my unit a few years back; I found myself translating the distance signs to the rest of the crew (exits were marked at 300, 600 and 1200 meters). My wife and mother-in-law took a trip south of the border a year or so ago, and all the signs down there were in metric, including the speed limit signs. Your Midwestern friends would find themselves in a target-rich environment the moment they crossed the U.S. border outbound.