D. Native Americans saw the survival of their traditional cultures threatened
Explanation:
The Americans were just plain disgusted by Native American's culture, beliefs, and lifestyle and viewed it as uncivilized, sinful, and savage-like, they forced the Native Americans to leave their culture behind and assimilate to a lifestyle that was seen as acceptable to the americans such as christianity, english literature, etc. Because of this the Native Americans felt threatened as they were being pulled away by their culture.
