1. Disease: The arrival of European settlers brought with it a host of diseases to which the Native Americans had no immunity, such as smallpox, measles, and influenza. These diseases decimated the Native American population and weakened their resistance to European encroachment.
2. Military Power: The United States military was far superior to that of the Native American tribes in terms of weaponry and organization. This made it difficult for the tribes to resist the US government's efforts to expand into their territories.
3. Cultural Disruption: The introduction of European culture and values disrupted traditional Native American ways of life. This led to a loss of cultural identity and a sense of powerlessness among many Native Americans.
4. Government Policies: The US government implemented a number of policies that were designed to assimilate Native Americans into white society. These policies included forced removal from their ancestral lands, the establishment of boarding schools for Native American children, and the outlawing of traditional religious practices.
5. Economic Dependency: The Native Americans became increasingly dependent on the US government for food, clothing, and other necessities. This made it difficult for them to maintain their independence and resist the government's efforts to control their lives.
As a result of these factors, the Native American tribes were eventually subdued and forced to live on reservations.