The UK is metric because they are not dumb (even the inventors of the imperial system have gone metric). America has been waffling about metrication for a long time. My information is that it was tried once. The government [USA] caved when everyone squealed. It is a hard and painful process and requires political will and the ability to bear the “slings and arrows of outrageous fortune” from an angry electorate. SA is metric and so is the rest of the world. It’s a rational unit of measurement and America should ‘bite the metrication bullet’. It must be the only non-metric country. Inconvenient (as they are so big). I remember the trauma when SA converted. I was a leading whiner for the status quo. I still think in both systems (pretty mixed-up but I am older and remember imperial). Height I think in ft. & inches, weight in kilograms (sometimes in lbs.), speed in kph. etc. MPH and gallons are simply bizarre (KPH and liters). Tons I need to know metric or otherwise. And so on. By any objective analysis, it is an extremely wise move. My children are totally metric. It has to be done. The longer America delays, the harder it becomes.
IMO America is crippling itself in a dire situation (financial crisis), by remaining imperial. This must impact their exports and imports. An importer needs a new set of tools for equipment issues (cars, etc.) and volume (gallons), weights (lbs. & ozs.), etc. The logistics are horrendous. America is imperial, the world is metric. This would imply a different tool set for American vehicles. If you lose a nut, you can’t delve into the scrap box (which every workshop has) looking for a nut that will fit. It won’t. Spares would be a nightmare (nothing would fit). Exporting other non-metric products will also have a negative impact on the USA. This is just an added burden when the USA is trying to make itself pretty for potential importers of goods. America is out-of-step with the rest of the world (which is metric).