Final answer:
The subjugation of American Indian tribes was driven by land acquisition, military dominance, and assimilation policies. The early U.S. sought land expansion, which led to treaties and removal acts, diminishing tribal sovereignty and forcing cultural assimilation.
Step-by-step explanation:
The most important factors that led to the subjugation of American Indian tribes in North America, particularly by the United States, include land acquisition policies, superior military power, and assimilation practices. The early U.S. Indian policy was driven by a strong motivation to acquire land, which was considered a crucial resource for the expanding nation. With the passing of the Indian Removal Act of 1830 and other governmental strategies, tribes were forced to cede their territories through treaties often concocted under duress or through outright seizure. Factors like the advanced weaponry of European settlers, disease, and the perceived cultural superiority that justified 'civilizing' campaigns also contributed immensely to the subjugation of Indigenous peoples. The term 'domestic dependent nations' came to define the relationship between the US government and Native tribes, further eroding their sovereignty. Eventually, the U.S. government shifted from an outright conquest to a combination of treaties and policies that aimed to assimilate Native Americans into mainstream American culture.