Judaism is ethno-nationalist because Jews regards themselves as a tribe. If your mother is a Jewess, then you are a racially Jew whether or not you practice Judaism. If you want to convert to Orthodox Judaism, you need to be sponsored by one of their number to be shown how to cook, live and worship as a member of that community which goes beyond just going to the synagogue on Saturdays.
Islam is civic nationalist because it has a much lower entry threshold, requiring only a declaration of belief ie "There is no God but God and Muhammad is His prophet" to become Muslim.
Millennial Woes is confusing white people with the nation. Supposing white people died of some mysterious and fatal disease that only affected white people. Britain as a nation would still exist, but it would be a nation of non-white people. You may well think that only white people represent the nation, but I have demonstrated by positing this hypothetical situation that this is not necessarily so since Britain would continue to be populated in the event that all white people disappeared for some reason. The non-white peoples would just move into the vacuum in the same way that the original Britons who got swamped by the other white peoples who invaded Britain moved to Cornwall and Wales - yes, those white people who have always been here for practical purposes but who really really hate the English.
It is absolutely imperative that there is a dominant culture, however, to give the nation its distinctive identity. This dominant culture must not be perceived to be degenerate by the newcomers, because that would make them reject and despise it.
You will find that all empires are civic nationalist proclaiming that all citizens have equal rights and are not to be discriminated on grounds of caste, race etc because it is a polite fiction that causes least resentment and obtains the most national unity. It is up to the dominant race and the dominant culture to perpetuate itself and maintain its dominance. I say this is a civic nationalist who is not white but does not wish to see the white race dominated by any other race. The dominant culture is not what it ought to be, and this is a matter for the dominant race to sort out, if it wishes to preserve its dominance.
As Andrew Breiitbart said, "Politics is downstream of culture."
If this is so, culture is downstream of law.
If this is so, law is downstream of morality.
If this is so, morality is downstream of religion.
Christianity has failed.