NWR depends on thousands of transmitters providing spotty coverage for most of the landmass of the USA. There are large unserved areas, but few people live in t

NWR depends on thousands of transmitters providing spotty coverage for most of the landmass of the USA. There are large unserved areas, but few people live in those areas. The main problem is that this requires that thousands of radio stations continue to operate, where a single AM station can provide service to multiple metro regions and in many cases cover an entire state. It would be even better if car radios were required to include shortwave / SSB receivers, but there is little mechanism to support the economic ecosystem that would keep those stations viable, and the radios are necessarily more expensive. The long range of shortwave would also open up US listening populations to potential foreign adversaries. AM is a good compromise. AM recovers are cheap and simple, transmitters can be made using 1920s tech, and A single AM broadcast station can have ranges of nearly 1000 miles, sometimes more.