Some of the nations are fairly large with full national stations. The fact is that local agencies don't have to buy each market individually but, instead, get every market, every rural area, every corner of the country with one buy.All smaller countries with much different laws and customs. Not comparable.
In fact, part of the reason for the creation of RDS was to allow national station on many, many frequencies to be automatically "found" based on the best signal at any location. So, if Cherie is on 250 transmitters all over France at lots of different dial positions, if you drive from Paris to Calais or to Bordeaux your car radio always seeks the best Cherie signal and locks it in while checking to see if there is a better alternative as you drive.
Agencies buy OTA TV through networks. And they don't buy individual stations, they buy CBS, NBC, ABC, Fox. One buy, one invoice, one spot.No TV company has that ownership either. Does TV have this kind of problem?
Local TV stations get all their local revenue with news and syndicated shows. The model is different for the station owner, but for national agencies with national accounts, they buy national shows.