Yes, DRM is being adopted in countries all over the world, but for some inexplicable reason, the U.S. always seems compelled to do things a different way. Maybe that's what they call "American Exceptionalism". In the U.S. the FCC has apparently carved in stone its commitment to so-called "HD radio", a proprietary digital system developed by iBiquity corporation.
Proponents of DRM claim it's more efficient and works better than the HD/iBiquity, plus broadcasters and receiver manufacturers wouldn't have to pay an annual licence fee to use open-source DRM technology. Limiting the broadcast industry to proprietary technology results in a monopoly of questionably legality; $$$ talks.
The common-sense approach (how often does the FCC ever go that route?) would be to allow volunteer stations to experimentally broadcast in DRM or HD, and see which actually works better, while allowing those stations to simulcast in analogue AM if they wanted to. After a certain peroid, the system with overall superior performance would be mandated as the digital standard, but if the HD system were chosen, in the exchange for the privilege, any continuing licensing fees following the initial purchase of hardware would be prohibited.
The AM band is already far too cluttered with little toy 250/1000 watt local stations stations, many of which don't even reach the city limits, and function essentially as satellite repeaters with few listeners. Letting those stations go dark would clear up the band for a smaller number of higher powered stations with regional daytime and nation-wide night-time coverage, and leave room in the band for experimental digital broadcasting.
The public are not going to rush out and purchase new receivers just to pick up the new digital broadcasts. Any form of digital would have to be phased in over a period of years or even decades, just like the expanded 1600-1700 kHz "expanded" AM band was phased in over the 1980s, 90s and 2000's.