From what I hear from a broadcasting group I am a member of that has many members in the USA, it seems that AM stations are closing steadily over there just as they are here and for similar reasons although there were more there to start with.
I own a 4 year old petrol car here in the UK that has no AM radio (Mini/BMW) - everything other than besides so it's not especially new.
Being a radio anorak I carry a small pocket sized AM/SW & FM radio (Tecsun) in the glove pocket to scan the AM band when out and about sometimes but I mostly listen to DAB when driving or Spotify.
Electric cars are driven by AC motors powered by an invertor from the batteries which causes a lot of local electrical noise. With a lot of scheming and screening it could be possible to make the noise floor so only weak stations would be affected badly it's probably thought that with it's decline in use it just isn't worth it when you consider that most who buy EV's are going to be tech savvy people who want new technology, not old.
Not a fan of EV's myself by the way and think there are way too many limitations to owning one and likely to be for years to come.