Also you kind of have to include the UK in the list of countries that use imperial measures. We're mostly metric but the roads are in miles/yards and if you tried to take pints (which are larger than American pints at 568ml) out of British pubs in favour of the smaller half-litre it would make the party that did it instantly unelectable. People are nearly always measured in feet and sometimes weighed in stone (14 lb) too. I'm a little surprised we don't measure fuel efficiency in miles to the litre because that would be pretty typical of the British approach to measuring things.
I actually don't think it's a bad thing, a bit of mental maths never hurt anyone and it underlines the fact that units of measurement aren't handed down on a stone tablet as a fact of nature.