Why was native american culture threatened

When European settlers arrived on the North American continent at the end of the fifteenth century, they encountered diverse Native American cultures—as many as 900,000 inhabitants with over 300 different languages. These people, whose ancestors crossed the land bridge from Asia in what may be considered the first North American immigration, were virtually destroyed by the subsequent immigration that created the United States.

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explanation:

the answer should be a. the sui empire, the tang empire extended from korea in the west to manchuria in the east.