You see, what you call the "standard" set of measures we call "imperial" measurements because that's literally how old it is! Some of them we were taught at school and we still use miles and weigh ourselves in stones and pounds (not just lbs so that needs some mental conversion) but elsewhere metric rules. And only my parents' generation and older use Fahrenheit.I was in elementary school from 1978 - 1983 (including kindergarten). Back then they made a push to convert the US from Fahrenheit / Standard to Celsius / Metric system. They taught both in school, and how to convert from one to the other and vice versa.
But it failed and we're still on Fahrenheit / Standard. I don't know if they even still teach Celsius / Metric, at least in elementary school....
Somewhat ironic that the U.S. stuck with imperial measures longer than England has Though, to be fair, you did invent your own gallon. It's smaller than ours, so mpg comparisons don't work.