I can only speak for labradors in UK, but that may be helpful.
There are several distinct sub-breeds:
The show labrador is bigger all round than the others, less working instinct, not so clever, and in my personal experience (may not be true for all) can have a dodgy temperament with other dogs (fine with people).
The working (gundog) labrador is short, chunky, compact, very clever, genial personality BUT needs to work or else have a lot of occupation.
The trials labrador is the same height as the worker, but much racier in build, very driven to the point of frantic for work, trainable to a high degree but challenging ("hard-going").
From what I hear, and I will be pleased to be put right if this is wrong, in USA working labs are usually trained by the shock collar and therefore the biddable temperament has not been bred-in as it is not needed. This might be the root of the observation that English labs are calmer.
However, English labs in England might be quite different from labs that are called English in USA (rather like American cocker spaniels and English ones in USA which are each totally differnet from working cockers in UK which are different again from show cockers in UK).
If you've read this far
and it isn't clear, ask me again and I'll try harder - but I hope it makes sense.