The example of inter tribal slavery doesn't actually apply to what I'm talking about. Slavery, and highly destructive, unprovoked raids which sometimes concluded with massacres of women and children were normal in the Americas. Is enslaving a member of another band or tribe a violation of trust? Is engaging in unprovoked war raids a violation of trust? These practices would not come as a surprise to anyone living within raiding territory of a warlike people. Trust can only come into play when a party to an agreement, whether tacit or explicit, has an opportunity to violate what was agreed upon.
Saying "Every nation ever has always tried win zero-sum interactions with other nations" conceals that there were actually vast differences in the way colonialist powers conducted themselves in relations with Native American tribes. The (at the time British) Canadian government honored treaties much more often and in better faith than US authorities.
My point is that in-group relations is not the same as out-group relations. High trust is about how you treat members of your in-group. Enslaving foreign people is most certainly a "low trust" move (how can I possibly enter an agreement with you when I know you might just show up one day and enslave me?) but it's fully possible and consistent for the perpetrator to belong to a high trust society.
Your example of the Maori is perfectly analogous to what happened in Canada/ But regardless of how things turned out, why did the British honor treaties when they had no incentive to do so? How do you account for this difference in a world dominated by purely rational decision making when interacting with those outside of your culture?