The advantage of am over fm is the simplicity of the electronic circuit.
In am its very easy to create a receiver to listen to broadcast. While an fm radio is too complicated for amature electronic.
So i dont belive am will ever be dropped for emergency radio
You can actually receive FM very simply. Here was an amusing post on Reddit [1] a few years ago from someone who was trying to make a simple audio amplifier and found that it was receiving his local NPR station which was broadcasting FM on 88.3 MHz. After some experimenting he got it down to just a cheap op amp, 2 capacitors, 1 potentiometer, a 9 V battery, a speaker, and some wire for an antenna.
It is working through slope detection. Basically if you've got FM at frequency X carrying voice and you measure the energy at a frequency a little bit away from X, as the FM signal frequency varies due to the voice modulation the energy you measure near X will vary in a similar way, so your voice modulation of the frequency X becomes amplitude modulation of your energy measurement.
You can play with this on an SDR, such as a cheap RTL-SDR dongle. Find an FM station and tune to its center frequency with your SDR software set for FM demodulation, and verify that you are indeed on an FM station broadcasting voice and/or music. Then switch the SDR software to AM demodulation and start slowly tuning away from the FM center frequency. You should find a point where you can clearly hear the voice and/or music. It won't sound great compared to FM demodulation of the same station, or compared to an AM station, but it should be serviceable for receiving emergency information.
FM radios aren't complicated at all. And FM transmitters, in particular, are extremely simple. When I was a student we had a tiny one we made in an afternoon (this was decades ago), we connected it to our 8-hour reel tape deck and had our own music station in the car radio when we drove around in the area.
The advantage of AM is, as was mentioned already, the lower frequency used by AM which means much better coverage. FM 87MHz-108MHz is almost just line of sight.
And how is that relevant to the alleged complexity of building an AM radio vs an FM one? The point was that the latter is easy, not complicated. The FM transmitter is so easy to make that you can make one by accident - if there's a non-linear element in the rf part.
So i dont belive am will ever be dropped for emergency radio