Oh I know many Volvos and Jags and Audis have the rear fog lamps -- even on US-spec models. But so relatively few high-end European cars are sold in the US, that 99% of American drivers would not even know what a rear fog lamp is, or why it might be useful. You don’t see rear fog lamps on VW models, do you?
For those European cars that do feature rear fog lamps, they are often switched on automatically when the front fog lamps are turned on - especially on Volvos. Useful in the home country, but the big problem is of course that switching on the front fog lights in perfectly clear weather long ago became a misguided fashion statement among the group of cretins who buy cars simply as status symbols. When the front fog lights are switched on to look “cool”, the driver doesn’t realize (or care) that the rear fog lamp is switched on as well. Following a car with the glare of 50W bright red rear fog lamp lit in clear weather tends to obscure the regular brake lights and is definitely dangerous.
My guess is that the MINI will not have the rear fog lamp activated for use on US-spec cars (and almost nobody will notice). BMW doesn’t provide rear fog lamps on US-spec models, do they?