It was commerce and the right of a state to freely engage. DC and the Northern states disagreed with the South.
The Mississippi River was a huge player in the Northern Aggression.
Understand history, not political BS from your “changing history 101” class.
Exactly how was it “commerce”. How did the Buchanan administration interfere with southern commerce. Did they forbid the South the right to sell cotton or tobacco to whom ever they pleased. Did they confiscate southern goods and products. Did the Buchanan administration order southern planters to stop farming cotton, tobacco, indigo or rice. Explain how it was commerce, if you can.