Following the 'American Dream' in the UK isn't the problem. No one I know in the UK wants that. It's hugely more nuanced than that. Culture requires groups of people with similar views, opinions, and values. And that goes to a very, very, local level. We now have expensive houses, a mobile population, a London-centric economy, and fractured and geographically spread families.
The decline in Christianity in the UK probably has something to do with it, and that in turn is loosely correlated with WWI and WWII. That's also another historic factor - families destroyed, and fewer families and so on.
And then the elephant in the room - London.
Want a job? Move to London or the south east and leave your family behind. Born in the south east? Want to live in the same street as you parents? No chance. Same town? Unlikely. Do you know your neighbours? Maybe. Do you see them in the church any more, or even when you walk down the street?
Culture is alive and well outside of London, despite its drain on the rest of the UK.
Social, and economic mobility is good, but some of the side effects are only now becoming apparent. Successive short-termist poor governance for decades has been the problem.