It's very interesting to see how people remain in smaller and more homogenous groups than they realise when it comes to dialect and speech habits
It is not a matter of "remaining" in any group. I'm an ex English teacher. In school we teach children to be able to recognise the difference between dialect ( regional variation), colloquialism, and standard english.
Language reflects culture, and also shapes it. I don't accept that American culture is the same as British culture, nor do I want it to be. British language and the various regional dialects ( & languages) have grown out of specific historic, social and cultural events & experiences.
And while exposure to American language and culture is the norm in Britain, due to the shared use of the english language and through subsequent exposure to, and the sharing of, music and cinematic art forms, I certainly, for one, will always resist this kind of cultural colonisation as it just doesn't sit well at all, and therefore feels fake.