A nation, in other words, is not a “community of values” or an impersonal social construct governed by certain laws. A nation – as the word suggests, derived as it is from the verb ‘to be born’ – is a family. A family can be a source of great love, indifference or even fratricidal conflict, just as a nation can experience cohesion, social exclusion or civil war. Nations can certainly welcome into their midst people who are not originally members of it, just as a family can expand to include in-laws. Both can and should show tolerance and friendship towards them. But at the end of the day, nations like families are bodies of people related to each other by blood.
This basic fact remains, whatever choices the individuals themselves may make. It does not absolutely determine human choice but it does influence it. The experience of second and third generation immigrants in Europe, whose parents or grandparents have chosen to come to a new country, and who have themselves chosen to remain in it, often shows the truth of this: in spite of their individual choice, people’s behaviour often remains ethnically based and culturally separate from that of the host nation, especially if they are of a different race.
Also worth reading is Mark Richardson's recent post on civic nationalism:
Civic nationalism has no future