Didn't France go metric a few centuries ago? Anyway, I suspect there are at least 10 times as many buildings, and 10000 times as many machines deployed, in 2026 America than the number you'd get by adding every European country's stats at the year they really seriously standardized metric.

You can make a better case that we were fools to not stay the course in the 1970s than a case that we should try it today. Even the 70s seem more like the very tail end of a window. 1776 would have been a great time to do it!