As a reminder, these are the three countries who don't use the incredibly sensible metric system: Liberia, Myanmar and of course, the United States of America. U-S-A! U-S-A! Hell, we should all form some sort of alliance! Non US-people, feel free to tell us why we're dumb for not using the metric system. [Wikimedia via ZME Science]
"feel free to tell us why we're dumb for not using the metric system."
Since you asked, there's 2 issues:
1. Everyone in the world buys and sells in metric, and then has to convert for the USA, we even screwed up the International Space Station!
2. Metric is base 10, conversion just require moving the decimal point, USC is insane with 3 hands to a foot, 3 feet to a yard, 22 yards to a chain, 10 chains in a furlong, and 8 furlongs in a mile. What is that?