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I don’t know if there is one good answer to your question since many factors at the receive site affect range, such as antenna, radio quality, man made and natural noise, and perhaps the greatest limit is due to co-channel interference (stations on the same frequency).
Maybe my experience will help. I chose a quiet frequency (daytime) in the 1600-1700 band for transmitting part 15 AM. I listened carefully and the frequency was quiet during the day. My receiver is a Yaesu FRG-100 and my antenna is a 80 foot long dipole 22 feet off the ground.
One day, I heard a “talking house” transmitter on my selected frequency. The signal was weak but clear. The home seller gave his address, and I checked it on a map. He was 2.7 miles from me. I happened to be driving toward his location one day and tried to pick up his signal on my truck radio. I could not hear him until I was about .2 miles from him.
The point is that even a good mobile radio which is better than a tabletop or portable receiver cannot come close to the capability of a communications grade receiver with a good antenna. Another point is that even though one hears their signal only so far on a car radio, the signal can be received at a greater distance with the proper gear.
Not many have the receiver setup that I do, but they are out there. I have mine for amateur radio and SWL use. Consider that few Part 15 AM stations can serve mobile listeners since they can drive through the coverage range in about a minute and the electrical noise in the typical house will bury a weak AM signal and part15 AM broadcasting doesn’t work well unless the population density puts many listeners in you strong signal area. If your intent is to broadcast to an audience, the potential number of listeners means more than just the range of the signal. Obviously the two are related but a 2 mile range in rural land has fewer potential listeners than a 2/10 mile range in the city.
Hope this helps.