how did policies and attitudes towards expansion impact native americans in the mid and late 19th century?

They were expelled from their lands

Explanation:

Voracious expansion policies in the 19th century encouraged the demonization of the native american tribes and caused many of them to be expelled from their ancestral lands and placed in reservations elsewhere.

The native american inhabitants of many of the territories that would later become states saw the land area of their nations severally reduced by the invasion of settlers and very rarely received just compensation.