"Nationalism" certainly is, as is the modern concept of the Nation-State. I can see the argument that "national identity" may predate this because of people identifying with their local empire or whatever, but that idea itself changed in very serious ways over the course of the world wars.
missed the edit, but: BTW, if you haven't watched the "Crash Course: World History" vids, they are awesome. Gloss over a lot of stuff to make 10 min vids, but really good for what they are.