While conservatives may not subjectively acknowledge this association, its consequences are clearly visible in the deepening ethnic divisions caused by nationalism in practice.
This is a non sequitur. Nationalism is practised by a society, not just conservatives. And even if you are correct here, nationalism is not synonymous with ethnicity, certainly not in the way you tried to conch it.
The idea that e.g. American nationalism can be totally disconnected from ethnicity...
You are building a strawman. Your claim was about conservative policies built on ethnicities. Conservatives themselves cover the entire range of ethnicities, with ethnic people often being the most conservative.
..often functions as an empty, ideological abstraction caused by the illusion that simply because two concepts can be semantically distinguished, they must therefore function independently in reality.
You are opposing claims that have not been made. You just agreed that the two concepts are not synonymous.
Basically, you are attempting to rationalize your way to the old liberal line that Conservatives are racist white men.
Some nations are ethnic groups (see ethnic nationalism) and some are not (see civic nationalism and multiculturalism)."
America is not a single ethnic group. And neither are conservatives. You are wrong generally, and wrong even more in the specific case of America.
In none of it's history has America been an ethno-state. And a close examination of actual history shows that conservative opposition to immigration has never been based on ethnicity (code for "race" with liberals) but on other practical factors.
Your question was rigged either knowingly or unknowingly to carry a liberal bias within it, to subtly cast conservatives as being motivated by racism.
Your strawmanning makes me suspect it was knowingly.
its consequences are clearly visible in the deepening ethnic divisions caused by nationalism in practice.
Others would say, "caused by unchecked immigration in practise." Outside of liberal bias, nationalism is not necessarily evil.