Kopikatsu said:
Because the internet is international and he broke US law for which the US can claim that Americans were using his site (And they probably were, too). I don't think any country other than the US would bother prosecuting in that situation though, whether it's because they don't care or because they don't have the pull to go through with it.
I'm gonna stop ya right there: no.
By that reasoning every time you've ever viewed anything pornographic you are hearby liable to be extradited to Libya to be tried there and punished. Furthermore if you've ever downloaded any DLC for your Xbox/PS3 via the internet you're also going to be extradited to China as those services are not allowed and you've committed a criminal act. Oh and if you've ever seen any funny pictures mocking the late Kim Jong-il you can be extradited to North Korea and be tried there and locked up for a decade.
Internet laws are subject to residence of the owner of the site and country the server is located. If someone's a British citizen and hosting a website with a server on British soil then America has no fucking jurisdiction whatsoever over that person or his website. The maximum they can do is inform the British authorities on the matter and they can procede accordingly depending on if he's actually broken any British laws and they can get American ISPs to block the website from their DNS databases. Much like how China gets its panties in a bunch over most of the internet instead they filter it from their citizens and not embark on a digital crusade to lock up everyone who is doing something illegal in their eyes.
Just because it's the good ol' U.S. of A doesn't give them any authority whatsoever to police the internet and be judge, jury, and executioner.