As a communist from Siberia, I believe that nationalism is always right-wing. It cannot be left-wing. Why should I love my nationality more than others? My nationality is an accident. If I had been born elsewhere, would I have to love another nationality? Why? Wouldn't it be better to love the proletariat and good people? If tomorrow all the inhabitants of the earth will be white or black or Asian, but they will be good people and will build communism, why should I fight it? Because we have to control the ratio of skin color to skull size? That doesn't smell good.
If I say my nation or nationality is great, it creates a system of relativity. There are great ones and then there are secondary ones. How can there be a great nation in a world where everyone is great?
In a world where there are no low can't be high, in a world where there is no evil can't exist good, etc..
Nationalism is always a right-wing ideology. Internationalism is a forced measure of survival under capitalism. But a True communist/socialist is always a cosmopolitan at heart. Every part of the earth is his home and every person on this earth is his people.
If the Vietnamese or American flag develops over Russia, but we live under communism, it will be our victory.
Because a communist fights not for form, but for content. The socialization of the means of production and the dictatorship of the proletariat. Including not for the appearance of man, flags, anthems, etc., etc.