(See the little triangles?)
My understanding is that the AM antenna has always been a small device within the radio, itself.
When AM reception stops being a concern for the car, the car will probably become a noisy emitter at those frequencies, which might make reception impossible.
I believe that the government has sunk a lot of money into emergency AM broadcasting. Oh, well. At least it wasn’t their money.
In a home radio - yes; but not in a car.
https://en.wikipedia.org/wiki/All_American_Five
(See the little triangles?)