I see. I think I didn't quite follow your question. You're asking why there aren't national radio stations. I think that has more to do with culture and the occasional practical issue. I often forget this, but you need to remember that the physical size of England is about the same as that of a medium sized US state. I think that folks here in North Carolina, for instance, would be less than interested in happenings in California. And advertising would be a nightmare, as most radio advertisers are smaller, usually regional, businesses. (And I'm not aware of any mutiple transmitter radio stations.)