Both nationalism and sectionalism increased during the era of good feelings how did both of these develop concurrently, and did one become of greater importance in the politics and economics of the period?

Nationalism enabled people to have a single strong government that fights for the United States of America. It developed sentiments of strength and unity in American ideals. Sectionalism on the other hand started developing around difficult questions such as slavery and opposed the strong national government because it didn't manage things like that. You could say that sectionalism became more important because it over the next 50 years sectionalist behavior more or less helped spark the Civil War which ended slavery completely.

This sentence is true.