SHORT ANSWER
What is the mass dispersion of a population from their homeland?

diaspora

Explanation:

is a scattered population whose origin lies in a separate geographic locale.

Historically, the word diaspora was used to refer to the involuntary mass dispersion of a population from its indigenous territories, in particular the dispersion of Jews

as general terms,  indian territory,  the indian territories, or  indian country  describe an evolving land area set aside by the  united states government  for the relocation of  native americans  who held  aboriginal title  to their land. in general, the tribes ceded land they occupied in exchange for  land grants  in 1803. the concept of an indian territory was an outcome of the 18th- and 19th-century policy of  indian removal. after the  civil war(1861–1865), the policy of the government was one of  assimilation.

it increased the power of the king of england.