[scroblart]

This is very weird comment. Are you saying that the USA was not a multi-ethnic/multi-religious state in the 1960s?

In a nation state, politics tend to be divided more on ideological and regional lines, because everyone shares an identity. There has never been a "nation" where everybody shares an identity in the sense discussed above.

[hyperdunc]

The comment makes sense, but the US isn't best example. Although last century the US was somewhat dominated by one identity (which is now waning and leaving room for others to grow) it has always been multi-ethnic and multi-religious.

A better example would be European nations like Hungary, which have reinforced their national identities in the face of the recent migrant crisis.