I know of 3 here in Las Vegas that came from my dealer in LA. Assuming for the heck of it that there are actually twice that number, and scaling for LV's 2.6M population to the US population of 328M, that suggests a wild ass guess of about 750 in the USA.
The same math from 5 cars in Washington state, and a population of 7.6M gives a second possibility of 215 cars. Seems too low.
