How did the early West cause a cultural transformation in the United States?

Mexicans and Americans were forced to live together after the Mexican War, resulting in a mix of cultures in the western United States
Because of the gold rush, many cultures came to the West and interacted with each other, resulting in cultural awareness for the United States.
The Transcontinental Railroad in the West allowed visits to foreign countries, and people were able to experience other cultures for the first time.
The U.S. purchased the Oregon Territory from Britain and Mexico, and those citizens still lived there after the purchase, mixing their culture with American culture there.