Yeah we were confused as hell when we pulled in for our first petrol stop on our US road-trip...
WHY IS THIS PUMP NOT WORKING!?
We found that when trying to pay with a credit card at the pump, it asked us to input our US zip code that matches where the card is registered, which obviously we couldn't do, so I don't see how we could have used our UK cards at the US pumps (is that all pumps that do the zip code thing or just some?)
All the pumps at major chain stations in the UK do have the credit card slot, but only a small minority of people use it, most pay by cash.
People who ARE paying by card still mostly go inside and pay at the till with their card.
And people who are using business fuel expense cards like lorry and van drivers have to go in to give the cashier the extra details.