(This ended up being a ridiculously long post so no worries if you don’t want to read it all but I think I do clear up and expand on a lot of things you’ve mentioned or asked about)

I think on the base level, the link to anarchism lies in the traditional cultural values and forms of organization of these societies took on pre-colonialism, which aren’t able to exist currently due to continued oppression and lack of sovereignty, but these values likely would manifest themselves if they had the space to since a decent amount of indigenous culture has been preserved through the last few centuries.

I’d also like to mention again that it’s really difficult to argue that indigenous nations are ethnostates because they are not states, they are comprised of people of a socially constructed class that was delegated as inferior - forced into this foreign class grouping through colonialism, and the nations which covered an area of a single ethnicity of people (due to natural historical and geological events) predate the notion of racial stratification that was brought in from europe. Indigenous people aren’t brought together by ethnicity, but by the shared experience of how they were treated through the process of colonialism. If following the treaties being honored, and sovereignty being returned to them, the portion of nations which currently do draw lines on ethnicity or heritage continue to do so, then you would be right in those individual cases, but going off of what I’ve seen, read and heard from the indigenous perspective, that’s not very likely to continue once the hand of direct colonial oppression is lifted and communities can rebuild.

On top of that, I think there’s definitely a tendency especially in recent decades for anarchist activism in colonized countries to take a focus on combatting not only systems of direct government control or economic structure, but also the systems of white supremacy and racism that have rooted itself in every facet of daily life through colonialism (one example which you commented on was race and census data, a surprising amount of which has its roots in the “skull size” theories of race from the 19th century) - For the sake of clarity, in most colonized countries, whiteness holds a different meaning than in Europe as it’s usually defined as being an absence of perceived physical and cultural qualities of the other (i.e. Black, Indigenous, Hispanic, etc. folk) instead of being defined on ethnicity and direct, traceable heritage. This is another example of how extensively colonialism has informed our social systems. - It’s important to recognize that it’s not the census policy itself that’s creating white supremacy and racism, but that the policy is a manifestation of those existing systems. Because of this, in the US there’s a good amount of mutual aid and democratic organization by anarchist groups that directly engage with aiding those who have been/are specifically targeted by these systems, rather than engaging indirectly through the lines of class.

I hope I didn’t come off as argumentative or combative because I definitely think there tends to be a hard-to-navigate disconnect in leftist thought and activism between european countries and the americas (both north and south) due to how differently colonialism and white supremacy has manifested itself in our modern societies. A lot of the time it’s hard to have both people be on the exact same page in conversation.

If you happen to be at all interested in reading some US-centric texts related to this then I could definitely recommend some but I know it’s already exhausting seeing so much of that perspective online