Confused I am. In the US, are there digital transmissions in the AM

Unfortunately, there are digital transmissions in the North American Medium Wave band , AKA, AM band.

iBiquity's in-band on-channel (IBOC) digital radio technology used by AM and FM radio stations.

A far as I’m concerned, it just makes a MW DXers life more difficult.

I can’t find a radio that receives HD AM.

I don’t know if they’re even made.

I think the HD format was introduced for Automobile Radios.

HD radio hasn’t gained wide spread acceptance.

As far as I know, there are no DRM broadcasts emanating on this side of the Pond.

I can’t even find a DRM  Receiver, except for SDR types.

I bet someone more knowledgeable on the subject can answer your inquiry better.

73 Gary Vance, Grand Ledge, Michigan U.S.A.

From Wikipedia

HD Radio is a trademarked term for iBiquity's in-band on-channel (IBOC) digital radio technology used by AM and FM radio stations to transmit audio and data by using a digital signal embedded “on-frequency” immediately above and below a station's standard analog signal, providing the means to listen to the same program in either HD (digital radio with less noise) or as a standard broadcast (analog radio with standard sound quality). The HD format also provides the means for a single radio station to simultaneously broadcast one or more different programs in addition to the program being transmitted on the radio station's analog channel.