I read a couple of comments to that effect on this Youtube video, which is basically a man ranting in Cockney from the movie Football Factory (2004). The comments bemoan American ignorance about the actual frequency of Cockney speakers, and suggest that it's all but disappeared amongst the working class except in a few areas. Saddening, if true. Is it? (I'm not looking for a thesis, just "man-on-the-street" type opinions.)
The following link probably tells more about Scouse than most people want to know:
Look here me old china, the East End has basically gone to the dogs - lucky if you can find someone who speaks English, forget about Cockney.
Most punters who still speak Cockney live in Essex, Kent, with a few old school Cockney Yiddish folk in North London (Barnett, Golders Green). The old school 'real' cockney lived within the sounds of the Bow Bells and as I say you won't even hear many people speaking English round there now days, let alone a dialectical variation. It's all Pakistani and Bengladeshi in the East End nowadays.
Sadley me old mucker, successive British government have allowed many parts of the UK turn into a ten ounce rump (a dump). If you complain about it in public you'll be painted as an anachronistic pariah. I've had people in my cab from all over the world speak about it, they can't believe what they see. It's proper 'chicken oriental' (mental) mate.