Sorry to ask, I don’t want to seem ignorant but I really don’t get it. Like, I saw a post on someone identifying as Norwegian-American and I thought of what another commenter said that most people don’t do the stuff Americans do and how most people will see them as American. But I see many Americans strongly identify with a culture they were raised with. Is it still okay for them to do that? What’s the point?
I think people make fun of it because to a non-American it comes across as deeply insecure. The trope is that the USA has no history of its own and so its people latch onto the smallest scraps of foreign heritage as a way to give themselves some cultural context and cachet.
I don’t think it’s invalid - in many cases the ancestry is genuine, even if distant/fractional. If it helps them find meaning or feel connected to something then I’ve got no issue with it. Humans like to feel connected to other humans, and it’s fun to discover that you have things in common.
The issues only really arise IMO if someone starts weaponising that ancestry or insisting they now have the authority to speak for a people they have no tangible connection to.