I thought there would at least be local community radios held by associations in the US. The way you’re describing this we’ve got pretty much the same situation in France where all the mainstream radios are owned by one of the few media groups, but that doesn’t stop local community radios from broadcasting for more than 50 years for some of them.
Mainly local radio broadcasts, sometimes thematic webradios such as Radio Metal. Recently I’ve been linking my music player to LastFM so we’ll see how it performs.