Man, every measurement the USA uses is screwed.
For Celcius vs Ferenheit. In Celcius 0 is freezing point and 100 is boiling point. Doesnt that just make sense?
For km to miles, first of all, kh/h is more accurate and can be broken down into perfect increments. i.e. 1 km = 1000 Meters = 100,000cm etc.
Why would you have 1 mile = 5,280ft = 63,360 inches etc????
After about 4,000 years of using standard units of measure, couldnt the whole world be using the same units for God's sake?
As for the USA, it seems like a matter of 1 part national pride, 2 parts stubbornness.