Sectionalism caused conflict in the United States during the early 1800s because they made a strong felt division between the North and the South of the country. There was a loyalty to one of those parts of the Nation, not to the Nation as a whole. Americans felt like Northerners or Southerners, not as Americans.
Another conflict was that the North wanted to get certain trade laws which favored them economically, but which did not favor the South, as both of them did not share the same living economics.
Today, sectionalism affects politics as there is a strong division between liberals and conservatives. It also affects economics in the way that the North devotes to technology, education, and modernization, while the South devotes to agricultural work.
