Final answer:
Native American civilizations were threatened by American settlers, diseases introduced by European colonizers, and government policies.
Step-by-step explanation:
Native American civilizations were threatened by various factors during the colonization of North America.
One major threat came from the American settlers who pushed westward and came into conflict with Native tribes that had long been living on the land. As settlers moved further into Native American territories, clashes, and attacks became more frequent. The settlers, with the support of local militias and later the federal government, sought to eliminate the tribes from the lands they desired, fundamentally changing the Native American way of life.
Another threat was the introduction of diseases by European colonizers. Native peoples had no immunity to these diseases and suffered devastating losses. Epidemics claimed the lives of a significant percentage of the native population, leading to the loss of knowledge, tradition, and future generations.
The government's policies also posed a threat to Native American civilizations. For example, the desire to confine Plains Indians to reservations, teach them to cultivate land like whites, and leave their traditional way of life behind disrupted their hunting and roaming patterns and undermined their autonomy.