It's time for national units to finally be put out to pasture. Both US units and UK units.
You are welcome to try to change all the street signs in the UK using miles, and all the speed limits using miles per hour, and I'll predict you'll have utter chaos because the percentage of drivers who can figure out that 80km/h = 50mph is quite low, and the percentage of drivers who can do that calculation in their head without taking their hands off the steering wheel and their eyes off the road is tiny.
We managed the changeover in Canada just fine.
But then again, we're like a younger, hipper, better looking version of the UK anyways....