And a monolithic entity which swallows its own retarded propaganda, at that. I don't think those assumptions work very well - they wouldn't be as effective as they are if their leadership were that blind to everything but their own nonsense, and they most certainly aren't a monolithic entity.

It's early days yet, and I may have missed it, but so far I haven't seen anything suggesting that the perpetrator had been to Syria. He was born in Britain, anyway. When it comes to preventing terrorism in Europe or the US, we could care less what happens in Syria; the key point is preventing the people who are already in Europe from radicalizing, even more than keeping an eye on those who returned from Syria. And while obviously there is no one solution to prevent people from radicalizing, there are certainly steps that can be taken to reduce the likelihood. Doesn't mean you'll stop it completely - but at this point nothing you do will stop it completely. Certainly not some battle in Dabiq.