When I was a college junior at Loyola Marymount University between 1983 and 1984, I took a business marketing class with Dr. Jim Bowie (he's now deceased) as professor. One of the things that Dr. Bowie told me and the entire class was that if you want to have free markets, then you must allow businesses to fail. And sometimes that includes whole industries!
I say all of that because what I'm about to say is done with a heavy heart. If the U.S. radio industry is dying, then we must let it die. No amount of propping up the industry (as
@davideduardo suggests) will allow the industry to ultimately survive and thrive, not even allowing stations to create national networks. The only thing I see national networks doing is possibly prolonging the inevitable.
I am very much in agreement with
@Theater of My Mind and the point he/she makes about why broadcast ownership rules shouldn't be loosened. There are only so many over-the-air frequencies available and, even if you narrowed the kHz frequencies to 9kHz apart (as is done outside of the Americas) and allowed broadcasters to broadcast on even numbered frequencies in the mHz band (such as 94.2), you *still* wouldn't have the current number of available places to listen as are on the Internet.
We humans tend to be a selfish and greedy lot, especially when it comes to business. We want it all. In another field and a few decades back, the Hunt brothers tried to "corner the market" on silver. Literally, these people (and they were actually brothers) tried to make it so that the only place both nationally and worldwide where people could purchase silver was through them. Fortunately, our government through legal enforcement stopped that.
Unfortunately, we are now in a situation today where the only option to "save" radio is to allow large corporations to gobble the smaller ones and create national networks like
@davideduardo saw in central and South America. If that is really the only solution to the problems faced by radio broadcasters, then I think the only thing to do is let the whole medium die. It was nice while it lasted, but maybe the best thing to do now is let it end.