So, in a car, the AM antenna is incorporated into the FM antenna?
In the 70’s I had a Toyota that only came with AM. Maybe it was “FM Ready”, since it had an antenna.
I have NO idea where it is in todays vehicles.
In our GC the FM went out after about two weeks after we bought it.
The AM worked.
The service folk said it was a bad antenna connection.
I never got to see the bad part(?).