It was too difficult, since it was easy for locals that knew the land to just run away and take refuge with other tribes. In Florida, some black slaves notoriou

It was too difficult, since it was easy for locals that knew the land to just run away and take refuge with other tribes. In Florida, some black slaves notoriously ran away and joined the Seminoles, a tribe that led a pretty notable resistance for sovereignty. This is a simplification, another big factor would have been the fact that many tribes had already established themselves as political entities, expect the five civilized tribes, via trade and intermixing. I would hazard that many white people from the south and southeast would have some native ancestry. Finally, when all blacks we're defacto slaves and free blacks were uncommon, it was easier to identify a run-away. In fact several Southeastern tribes owned slaves themselves and the Cherokee were actually split in their support for the Union vs the Confederacy.