It seems that the US is the only country that uses the month/day/year format, everyone else uses either day/month/year or year/month/day. I can see the logic in the latter two, but none in the former.
If you're in the market for a new car, the economy will be almost certainly quoted in miles per gallon.
But once you've bought your car, if you go to buy some diesel or petrol (gasoline) for it, it will be sold in litres, not gallons. This makes no sense!
I suppose in the UK the mentality goes -- I've paid my Road Tax to use the WHOLE ROAD -- so why should I be restricted to using only HALF of it while driving - often seems like that when I'm unfortunate enough to have to use that country's vastly congested motorway system where every driver seems to think that they OWN the middle lane of a 3 lane highway whatever the state of traffic or however fast or slow they are driving.
However - if they want to restart the economy over there really quickly just initiate a program of switching to driving on the same side of the road as almost the rest of the planet does -- think of the small businesses / engineering / sign writers etc etc who would be employed for YEARS in preparing for the changeover -- I'll bet they'd switch to having the HIGHEST growth rate in the WORLD for YEARS and the lowest unemployment too. Cheaper than paying Billions to despicable Banks who are still re-possessing people's homes at an alarming rate and then flogging them off CHEAP to their buddies.
As far as the US is concerned there is often a "Not invented here-- so I don't want to use" mentality -- remember things like Incompatible Mobile phone systems, etc and particularly the NTSC TV system --I still remember those men with Green / purplish faces etc on the screens -- the system was popularly known as Never The Same Colour !!.
However attitudes are gradually changing although traces of their mentality still exist -- such as UTC instead of GMT and in a lot of Movies where "History" is often re-written for domestic cinema audience consumption.
Looking at the diagram Metric seems to make a lot of sense. So, what happened back in the 70's when the US was suppose to start moving everything over to it? Corporations and republicans HOWLED and prevented it. Because Jesus doesn't approve I guess.