I am highly skeptical of the earlier claim that 80 million Americans listen to AM radio weekly. When including other methods to access AM stations' content such as streaming and FM translators, that figure may be true.
It comes right out of Nielsen cume data for rated markets.
Yes, it may contain streaming data if the stream is a 100% simulcast.
And, yes, it can contain translator listening. But in nearly all rated markets, translators do not account for a high share of listening as their coverage is so limited. There are a few markets, like Albuquerque, where there is a group of significant translators on a high location, but in few other markets is the share of AMs with translators anything more than a couple of percent.
Reception is terrible on the AM band, and in many cars (such as my own), the audio fidelity on the AM band also sounds like complete garbage. In my case, it's no big deal since I access AM station simulcasts on FM HD2 channels. The NAB should concentrate as much if not more energy trying to improve manufacturing standards for in-car radio units and reducing susceptibility to interference sources if it truly cares about preserving AM radio's long-term viability.
Efforts like that have been tried over and over, going back to trying to get the government to require FM in all radios, ideas about having FM stereo required, AM analog stereo, IBOC AM stereo and the like. The only case where there was no suggestion to get government intervention was, fortunately, quadraphonic.
Inclusion of the FM band, the shortwave band, and the weather band on car audio receivers is not mandatory. AM radio should not be given any special treatment.
The concept behind requiring AM is that it is the only radio service capable of providing information to a totally devastated area where there is no local media broadcasting, limited or no phone and cell phone service, etcetera. AM signals are capable of being heard from over a hundred miles away in the daytime and a thousand or more at night.
There is a counter argument that most AM stations have no news department and can't provide service. To the contrary, the emergency broadcast system allows "authorities" at the governmental level to issue notices and provide information directly, irrespective of the normal content of those stations.
I'll repeat the case of one of the worst hurricanes in recorded history in 2017 in Puerto Rico where one AM station gave ongoing coverage and information when there were no TV station on the air, no FMs, no cell phones, no landlines, no electricity for up to several months in some areas and for quite a few entire days everywhere. Similarly, it was the reinforced WWL in New Orleans that provided service initially after that city's hurricane and flooding when no other media was available.