I mean for literally a hundred years, almost all AM equipment has been in mono, including what you have in your car. The same signal goes to both speakers. You don't need to collapse anything because it was mono already.
The defining feature of Dolby Atmos is that it's a multi-channel format. You can't hear Dolby Atmos in a format that isn't compatible with it.
Furthermore, the maximum sampling rate is equivalent to about 12 kHz. The quality is extremely poor. It's really not worth talking about Dolby Atmos in the same sentence.