The reason road distances are retained in miles in the UK is probably because it would be so expensive to change all road signs etc to kilometres. But in any case, there is a great deal of resistance to metrication in the UK. For example, even though supermarkets now sell fruit and veg by Kg, in the London street market where I shop, the stalls still sell in pounds - though they do show the price in Kg as well. As for the US, it is in many ways a very conservative country, especially with George W Bush as President. For instance, as well as its retention of pounds, miles etc, any attempt to tamper with the design of US banknotes - which have been much the same for yonks -is fiercely resisted; then there's all the fuss about abortion etc etc.