How was the idea of Manifest Destiny brought about by nationalism?

Nationalism, or the belief that the United States was the most superior nation in the world, mostly drove the movement known as Manifest Destiny. Manifest Destiny was the belief that Americans had a God-given and ordained right to rule North America from the Atlantic Ocean to the Pacific Ocean.

in the 1950s, country music came into its own before rock-n-roll took off in the 60s while jazz and classical music continued to innovate