English engineering units were 'invented' by 10,000 different scientists/engineers in 10,000 different labs/conditions, mostly in England (Surprise!). There were a few 'conferences' held in Europe, and the metric system was founded (or Systeme International d'Unites). Here's the deal with Farenheit and Celcius.
It takes 1 British thermal Unit (BTU) of energy, to raise the temperature of 1 pound mass pure water (H2O), 1 degree Farenheit. There's actually a specific temperature reference, like from 34 to 35 degrees Farenheit, but I can't remember the temperature.
It takes 1 Joule of energy to raise the temperature of 1 mL of pure water by 1 degree Celcius. Again there's a specific temperature reference, but it escapes me.
Metric units use a mechanical basis, which makes conversions from thermal/electrical/mechanical just a movement of the decimal. It's much easier for me to think/convert/extropolate in metic than it is in english. You use exponents quite a bit more with metric calculations, and prefixes are used extensively (Mega, Giga, Tera, milli, micro, nano)
But if distances in America were suddenly given in meters/kilometers, there would be food shortages, riots, satellites crashing into Mars, gasoline price wars, prison overpopulation, etc. Mass Hysteria?