Many Americans think that all Brits sound the same, when the truth is that Britain has a range of accents, just like America does. A Southerner does not sound like a Brooklynite, for example, the same way someone from Newcastle doesn’t talk like someone from Somerset. I’d actually say that there are more accents across Britain* than there are in the States, but without actually experiencing the accents it’s hard to understand all the various ways people talk.
A Scottish guy on YouTube has made an 8-minute video explaining pretty much all of the different British accents in a pretty amusing way. Even with a heavy Scottish accent he’s able to very closely emulate the Essex, Cockney, Brummie, Manchester and other accents. The only accents I’d say he doesnt get quite right are the Welsh and Midlands (Derby) accents and probably the rural Irish accents.
* Keep in mind that ‘Britain’ includes Northern Ireland, Scotland and Wales, as well as all of England…which isn’t just London. 😉