The high instance of disease spread from Europeans to American Indian populations
was studied by European physicians and led to better
understanding of the behavior of communicable
disease.
drove surviving tribes to ally with each other to
strengthen their resistance to European invasion.
O weakened American Indian tribes significantly,
making them more vulnerable to European invasion.
led large numbers of American Indians to seek
conversion to Christianity, believing that the disease
was a punishment from God.

The high incidence of disease spread from Europeans to

American Indian populations

weakened American Indian tribes significantly,  making them more vulnerable to European invasion.

Explanation:

The population of American Indian tribes was greatly decimated by diseases, especially smallpox and other communicable diseases.  Most of the diseases were brought by the Europeans who had developed immunity to the diseases, and as a result did not suffer from the diseases but were able to spread the diseases whenever they had contact with the native Indian tribes.

Explanation:

Between 1828 and 1838, over 80,000 Native Americans were forced out of their homes to live west of the Mississippi River. Parts of Oklahoma were considered the Indian Territory. Currently, Oklahoma and California have the two highest Native-American populations.