That is, in part, because of the confusion in the terms "nation," "country," "state," and "nation-state." When Hindenburg spoke of the "German Nation" (Blud und Boten), he was talking about more than one country. One can speak of the "Cherokee nation" and not be talking about a political entity, but rather, a cultural one.
With that said, tribal treaties with the CSA are no more valid that confederate money.
Which means that Indian treaties with the US are invalid as well </sarcasm>