This has nothing to do with the subject other than a correlation coming to mind. I was a visitor here when I got a really bad earache. I went in to the local surgery, and although they treated me, no question, they didn't quite know how to charge me. "Uhhh, let's call it five quid," is basically the reaction I got. And I left with the nurses still scratching their heads as to how to handle an American tourist needing medical treatment.
That was a few years ago, and I think as more and more circumstances arise, these questions become more easily answered.
What makes sense to me, but is by far NOT the answer to rely on as being correct, it's not new that American tourists do something that causes a traffic problem. I think the solution has always been to charge a steep fine and then be done with it. What is new/different is that the same American will get a UK driving license as a resident. And I think this is the issue that's been left unanswered. My conclusion: the stiff fine covers it for the infraction made on an American license. On a newly issued UK license, the counter starts back at Zero. And that seems to be the easiest answer..."Uhhh, let's call it five quid".