Umm America is an ideological state. Civic nationalism is an ideology you agree to follow the laws, and support the underlying foundation of the nation and you are considered a true whatever. In America's case it's the constitution support of freedom of speech, the right to own guns, free press, free religion, Pro democracy/Republicanism, anti monarchy etc. That's why going against all that stuff is called unamerican, an ideology is something anyone can be a part of, you just have to agree to it and want to be part of it. An ethnicity is diffrent you can't really "convert" to another ethnic group, I can never become a Jew, a Japanese, or a Kurd unless I was born into that culture. But an American can be anyone from anywhere in the world who moves here, and goes through the steps to get citizenship. And it's ok to have an ideological state, however if all nations were ideological nations there would not be almost 200 of them there aren't that many ideological belief's out there.
Also no again ethno nationalism has nothing to do with white nationalism. Even if an ethno nationalist is from Europe it does not mean he is pro white or anti black or whatever. A polish ethno nationalist won't be going out and hating on blacks or asians or even be interacting with them so he can't be racist against them. A polish nationalist would be worried about the very real threat of Russia and Germany both groups that have in the past gone after their nation and attacked them. They would not be hating on or oppressing black, brown, or other people. As for the example of the Hutu that's because I know very little about African tribes, I know there are quite a few of them, but I can only really name the Hutu, Tutsi, Zulu, Yoruba, and I think xosha though that last one I mispelled. Xhosa think that's it. And I know almost nothing of their cultures or such. And I don't need to I don't interact with them, and they don't interact with me. I'm pretty sure a common/average Yoruba person won't know about Czech people, or Hungarians, or Sami, or Ukranians. And they don't need to, since they won't interact with them. There are thousands of different unique ethnic groups in the world it would be impossible to know each and every one of them.
Also it's not an immoral or intellectually bankrupt position, it's very logical for people to want to have political and military control of lands where they are basically the sole inhabitants of, it's intellectually dishonest to stick your head in the sand and not pay attention to the outside world and notice that there are groups that would want to wipe out certain ethnicities and those ethnic groups have to be wary of it. For example it's not unreasonable for Polish people to see Germany in the 30's after Hitler was elected and start to worry, about someone who thinks they are subhuman and wants their land. That means they need to watch out and recognize that Germans are not friends to the Polish people, they were fucked also because Stalin was on the other side and also fucked over Poland for Russia's bennefit. So a Polish nationalist needs to see that Germany is not a friend to Poland and Russia is not a friend to Poland they both want Polish lands and resources and to dominate Poland.