Yep, FM has a limited range compared to AM, but RDS cannot be used on AM.
The range problem with FM is overcome by using multiple transmitters, the problem then is that the transmitters that overlap need to be on different frequencies to stop interference, hence the use of RDS-AF feature to switch to the strongest signal.
Still doesn't explain why there are only local radio stations in the US. Although I do prefer the local radio here to the likes of Radio City in Liverpool !
The diversity of sounds here is amazing, if you can't find music you like here in Austin then there is something wrong with you