Just a form of clinging. Even conventionally patriotism is a form of indoctrination, or propaganda.
Look at it this way, we are stuck (imprisoned) in a meat suit (human body) on a floating rock (the earth) in the middle of the darkness (the universe) to then label areas of land on that floating rock, and then to identify that land with a symbolic pattern (a flag) and then to cling to that pattern as a projection of "I/me" is the mark of an imbecile!
This labelling of phenomena can be deduced to the microcosm of the microbiotic or sub atomic level, up the the macrocosm of galaxies, universe(es) and dimensions...With this understanding (sunyata) it would be absurd to cling to such a small part of that existence as a "thing" a country, and as mine.... a country is just a mental construct!, an idea. Clinging to this idea would only cause ruin.