Question

what are two ways in which sectionalism caused conflict or tension in the United States during the early 1800s?

Answer 1

First know that Sectionalism is defined as loyalty to a specific region or state in a country, rather than loyalty to country as a whole. (Usually referring to the separation of North and South in United States history)
From there, you can say that the separation caused a conflict of values and morals for the country (to own slaves or not to own slaves)
You can also say that economic differences (North more industrial, South more agricultural) and how they were going to build the country's wealth
(North wanted to function by trading within the country by creating the textiles and other industrial necessities for the South, and the South would grow the crops [food, cotton, tobacco] While the South believed England trading products were finer and wanted those. That's when they put a tax on imported products, which the South didn't like.