American cars for the U.K.
I think that they have never had much hold for the market: they used to be too large, and too heavy on very expensive petrol. Petrol was always expensive in Britain, at least from '56 when I started driving.
Ford eventually made a rhd Mustang, and now it faces being made uncompetitive with better-made, hot European cars. Its US heritage/romantic cachet may not be enough any longer. That is, unless Brexit makes everything uncompetitive. I can almost imagine Red Robbo coming back to life in some resurrected British Leyland adventure... beware, Pittsburgh, what you wish!
One of the Kray Twin wives had an American car... (I think it was one of the last cars that were made to Italian design by the company that grew out of the dead Studebaker)* a few other folks, mainly in the other showbiz with music and cameras, had them too, but usually people went for Jaguar and the local uber-brands that are still made in Britain, even if not actually owned by us anymore. Some went German and some Italian, too.
I am still nostalgic for US cars, but during my impressionable years I lived in India, and V8 was daily transport when I was out of prison boarding school, so maybe I see life from a different perspective. India may have been in Britain's immediate sphere of influence, but there were more US cars and magazines around than anything else that I can remember.
* Apparently not: seems to have been a Barracuda from Plymouth!