We’re taught both metric and US customary units in school. I prefer metric for most things, to the point I have a metric-only tape measure among other things.
However, I’ll die on the hill that Fahrenheit is superior for ambient air temperature. 0 degrees to 100 degrees neatly encompasses the range of average surface temperatures seen throughout the year in the contiguous US.
Most people with half a brain. Besides, road signs was just one example about cost, not feasability. Other industries, like construction, have a whole lot more invested in specific units.
Again, yes it’s possible to switch, and I think it’d be worth it, but… again, go convince those industries that do everything possible to save pennies per product and tell them they have to change…