I don't know what the situation is like in the US, but I was shocked to discover that there are no AM stations in my part of Canada. It is cool in tje sense that I can direct my antenna and pick up stations in Newfoundland and New York on a good evening, without dealing with interference from local stationd, but it would be positively useless in emergency situations. Even if distant stations broadcast useful information during an emergency, picking it up in a vehicle is unreliable. If the antenna is directional, the strength of the signal is going to vary wildly based upon the vehicle's orientation. If the antenna is not directional, you are going to have trouble with interference.
Don't get me wrong, I absolutely believe that broadcast radio is an essential tool during emergencies. I buy phones with FM receivers and have backup battery packs. I have an AM/FM/SW reveiver with backup batteries. I have a VHF transceiver, and am licensed to use it in both amateur and maritime bands. But, realistically, I don't see how most people would benefit from the few advantages that the AM broadcast band offers. You would likely be better off improving the resiliance of FM broadcast infrastructure. Even then one must accept its days are numbered.
Don't get me wrong, I absolutely believe that broadcast radio is an essential tool during emergencies. I buy phones with FM receivers and have backup battery packs. I have an AM/FM/SW reveiver with backup batteries. I have a VHF transceiver, and am licensed to use it in both amateur and maritime bands. But, realistically, I don't see how most people would benefit from the few advantages that the AM broadcast band offers. You would likely be better off improving the resiliance of FM broadcast infrastructure. Even then one must accept its days are numbered.