they are not intrinsically members of a nation and the support of that nation does not translate into their liberation.

That is what's traditionally known as "The National Question" and it's a lot more debatable and nuanced than you give it credit for.

Let's take the example of Ireland, which was much discussed by various Marxists historically. The movement for Irish independence was not inherently socialist, and the resulting state was still a capitalist system. It was defined more along the lines of nationality than class. However, under the existing system, Ireland had been horribly exploited and abused by the English, and so, this raises the question of whether socialists ought to lend support to such a movement, even though it is not ideologically pure. This is, of course, not something that is specific to Ireland.

Practically speaking, many struggles for independence have historically been more national in character. Frantz Fanon, for instance, was one Marxist who argued strongly for supporting such national liberation movements, observing that oppressed cultures can be stifled in psychological and cultural development because all they can think of is to be free of foreign control. Furthermore, the disparity between the rich and the poor of a colonized country may be less than that of the disparity between colonizer and colonized, and therefore an alliance along class lines can be permissible. Only after removing the pressing outside problem does internal class conflict emerge (and with it class consciousness), and until then it is unreasonable to expect the proletariat of a colonized country to recognize common cause with the proletariat of a colonizing country, especially if said proletariat does not emphatically support decolonization.

In general, this idea that "everyone is included under the conception of the international proletariat" moves away from practical, materialist questions and towards abstract, idealist principles. The national question is very much a relevant and important question in the modern day. Yes, we can all say, "I support the liberation of the Iranian proletariat just like the proletariat of every country" but one person might "support Iranian liberation" through bombing the shit out of them, while another might support leaving them alone and letting them deal with their government on their own, in their own time.

Eventually and ideally, socialists are broadly agreed that in time national distinctions will fade away and become unimportant and irrelevant. However, this must be done voluntarily. If the oppressed are expected to give up their cultural or national identities in order to receive support from socialists in oppressor countries, than this expectation is, and will be seen as, just another foreign imposition.

It was removed by the mod here. It was the astronaut 'Always was' meme saying that the DPRK was the most actually democratic country in the world. Glorifying a dictatorship.