Simon:
You make more errors in the UK because you’re on ‘home’ turf, so more relaxed.When I first ventured over the water I had a piece of card folded to just the right size so it would sit in easy view on top of my dash board.
It had a [ZB] OFF big arrow on it. I turned it over to point at whichever side of the road I was supposed to be driving on .
Even so, in my car usually, I’ve driven out of a one-way street, or a garage, or something similar and pulled out onto the wrong side of the road.
The home turf explanation make the most sense to me and although readers may find your arrow idea a bit corny I think it is a great idea.
When I became “temporarily unsure” of what side of the road I should be on it was absolute and total confusion.
You think you are right but something isn’t adding up and you are desperately and urgently looking for clues to confirm if you are right or in the wrong.
Your arrow would be the business in this situation as every second counts or might even prevent the mistake in the first instance.
At least I find the lane positioning fine but like The Bear the first few minutes after swapping from car to wagon or vav need care. Phoning the girlfriend straight away could indeed become expensive 