British domination of podcasts?

I have just been browsing through the Top100 subscribed podcasts and realised that British shows make up 19 of the top 25. It includes programming from the BBC, Xfm, The Guardian and The Times. Is there some particular reson that American podcasts are so rare, is iTunes only giving me the top 100 for the UK? Or is it perhaps onerous copyright law and aggressive litigation that keeps American shows from creating compelling content, or is it simply that the British are putting out better content. With my recent experience of radio stations in the USA, this does not seem at all unlikely.