How were Native Americans affected by westward expansion?

They were conscripted into the Union army.

They signed peace treaties that all sides respected.

They faced the loss of a major food source due to buffalo hunting.

They were forced to move to Mexico.

The Native Americans were badly affected by westward expansion as they faced the loss of a major food source due to buffalo hunting.

Explanation:

After the gradual westward expansion that occurred over a few years, the new white settlers began hunting buffaloes for their thick hides. Within a few years of hunting carried out by the white settlers, a large population of the buffaloes disappeared. These populations of buffaloes served as a source of food for the Native Americans which were no longer available due to extensive hunting carried out by the white settlers.