What was one impact of westward expansion in the United States during the mid-nineteenth century?

A decline in Native American populations in the region.

Explanation:

Native Americans were being exposed to and wiped out by diseases from settlers. They were also targeted. Gold was also discovered and big boom towns sprang up.

b. major john c. frémont led a rebellion called the bear flag revolt.

explanation:

during the bear flag revolt, from june to july 1846, a small group of american settlers in california rebelled against the mexican government and proclaimed california an independent republic. the republic was short-lived because soon after the bear flag was raised, the u.s. military began occupying california, which went on to join the union in 1850. the bear flag became the official state flag in 1911.

(b) britain had a much larger navy than the u.s.

(d) the u.s. had a small army compared to britain.