What is something that happened to Mexican Americans only during westward expansion?

Westward expansion began in earnest in 1803. Thomas Jefferson negotiated a treaty with France in which the United States paid France $15 million for the Louisiana Territory – 828,000 square miles of land west of the Mississippi River – effectively doubling the size of the young nation.

Hopes it helps

Explanation:

Polk declared war against Mexico, falsely claiming that the Mexican army had "invaded our territory and shed American blood on American soil.” The war proved to be relatively unpopular, in part because many Northerners objected to what they saw as a war to expand the “slaveocracy.”

*this may be the wrong thing you were looking for*

*that may be the wrong were but idc*

answer; /// i believe that the correct answer is (d)the huang he river valley;