undomesticable

I don't know how this fits into your theory, other than to say it's not that N.A. animals were undomesticable, rather that people chose not to domesticate them.

The Uncontrollable Controller Sage 2009

It is clearly a reasonable supposition that some of these primitive canine species may have been far more domesticable than the existing kindred of the dog -- the wolves, foxes, jackals, or hyenas -- differing from their fiercer kindred much as the zebras do from the wild asses, the one form being utterly undomesticable, and the other lending its back almost willingly to the burdens which man chooses to impose.

Domesticated Animals Their Relation to Man and to his Advancement in Civilization Nathaniel Southgate Shaler 1873

Our American bison, though a much milder-spirited beast, seems also to be essentially undomesticable for the reason that he cannot be taught to subordinate his desires to the will of man.

Domesticated Animals Their Relation to Man and to his Advancement in Civilization Nathaniel Southgate Shaler 1873