You might be surprised to learn that some US AM stations operated by state governments or Universities.  Their licenses state they are non-commercial AM stations.  The examples I am most familiar with are here in Wisconsin:  WHA Madison (University of Wisconsin) and WLBL Auburndale  (State of Wisconsin).   Others off the top of my head is WILL at University of Illinois, WOI Ames, Iowa (Iowa State University) and WSUI in Iowa City (University of Iowa)