what do you think were the major reasons why acculturation did not work with native americans?

This is because the whites made it impossible for Native Indians to acculturate. Segregating them on reserves was just one example of this,

“No matter how thoroughly Native Americans acculturated, they could not succeed in white society. Whites would not let them.... Indians were always regarded as aliens, and were rarely allowed to live within white society except on its periphery.”   pg 130