I would recommend on finding smaller AM talk radio stations to pitch your show to. First, listen to the station to find out if they actually play any local content as a lot of them just pull a satellite feed these days. Second, put a demo together on an audio CD and take it to the radio station office for them to listen to. Third, follow up.
You'll probably have to start out by doing the show for free (or a small percentage of ad revenue if you're lucky) and once you've done a few shows talk to the PD to find out if they have any connections with network providers.
As one example, I was involved with a computer show that started out just doing a 1 hour show Saturday mornings, they got a few shows together and emailed them to a small network provider (ones like TalkStar Radio or Accent Radio Network) and got a spot. Granted, the network feeds were one week delayed from the live program, but it was an awesome "in".
You won't be able to start with SuperRadio/Jones/USA Radio, but if you have a good show it shouldn't be hard to grow to that level.
