I think there is a lot of truth in that. It led to the death of patriotism (which is now considered embarrassing outside of sport), national purpose, institutions, empire, and coincided with the decline of heavy industry (which only happened much more recently in the US).

EDIT: Saying that, there is still a strong positive national identity. We're just too embarrassed to express it strongly (see patriotism), because of our fall from grace.

Going by the variety of flags i see people flying I'd say there is quite a lot of patriotism about - just not for the UK.