yes, agree. At one point the concept of international proletarian solidarity was prevalent- in fact its one of the founding principles of Marxism, that nation states were a imperialist concept dreamt up by the ruling classes on the principle of divide and rule. Class unity was more important than 'national' identity, and people's tendency to pick a date when their preferred nationality was in the ascendancy and try and impose that historic structure on their neighbours was seen as very dangerous*.
Which is one of the reasons Soviet nationalities policy is so interesting- it vacillated between attempting (with varying degrees of ruthlessness) to suppress all nationalist sentiment, to encouraging it and providing funding and degrees of independence to the member states. There are loads of themes including the movement of peoples across the Soviet union to dilute or reinforce national identities, moving internal borders to control access to wealth,infrastructure etc, forced settlement of nomadic people, settlement of previously uninhabited areas and so on.
* correctly- just look at the Caucasus. The Armenians seem to think they should rule most of it on the basis of a historical empire around the beginning of the spread of Christianity, every tiny tribe is seceding to produce (largely unviable) nation states, all of whom have to be a client state of someone to survive, be it Russia or Azerbaijan…. its a real mess. But it also suggests that suppressing nationalism because its dangerous doesn't make it go away. Or maybe to was the inconsistency of the suppression that meant it didn't die out completely. Dunno. Maybe I need to go any do another silly little university course