How did nationalism affect foreign policy in the 1800's?

Southern politicians (and many of their northern counterparts) had come to equate the expansion of a southern political power. Countering this sectionalism was the growing spirit of nationalism and the emergence of two parties, both with a national following. These developments seemed to overshadow sectional concerns, and with the election of Andrew Jackson, one of the most popular political figures since George Washington, the nation seemed more concerned with unity than division.