You can critically support left wing nationalism. The Algerian liberation movement was a nationalist effort that resulted in Algeria no longer being a colony of France. Of course, Algeria is not a communist utopia, they are still ruled by their bourgeoise, but the lives of average Algerians are indubitably better now than when it was a colony, just as lives of poor Native Americans would be better if they also were not ruled by the settler colonialists who are still doing genocide to them.

I still don't get your jump from "stolen land" to "national liberation". Left nationalisms don't use the Land Back rhetoric, neither do Land Back activists necessarily talk about national liberation. Land Back is about stewardship of land, not about a Native American nation state. And while I would prefer a No State solution for South West Asia (or the whole world), this doesn't stop me from rallying with people who demand a binational One State solution.

There is more than one battle to fight and while I respect that people pick one battle, we need solidarity and synergy between them. I see a lot of harm in your class reductionist approach. Everything that goes against the most privileged of the oppressed groups divides the working class. No, being against imperialism doesn't make me a nationalist.

And I still don't get why you brought up Israel. What is your idea? Would it benefit the Palestinians if they focused more on the white working class of the global north?

"stolen land" presupposes that land is somehow inherently private property of ethnic groups

No because there are other ways of ownership and other ways of relating to land that private property.