Hello! I don't need any help answering the question, but I tend to ramble on when I type, and want to make sure my answer is clear. Can someone help me summarise this?

What is the connection between sectionalism, slavery, and states’ rights as causes of the Civil War? How did the Southern response to the 1860 election results demonstrate this connection?

Sectionalism, slavery, and states rights as the causes of the civil war were all connected because the south practiced sectionalism because they were more concerned with keeping slavery (even to the point of secession, which they claimed was a state right) than with the well being of the other sections of the country or the country as a whole. The north also practiced sectionalism because (after the Kansas-Nebraska Act) they became unwilling to compromise with the south and disagreed with the south's views on slavery and did not believe secession was a state right. The southern response to the 1860 election results demonstrates this connection because the south seceded because they were afraid that the north would outlaw slavery(and thus practice sectionalism), so they took advantage of their "state right" and seceded.

As I said, I don't need any help with the answer. (As far as I know) but can someone help me summarize?

Whenever you believe you have finished writing an assignment, you should run it through www.grammarly.com to see what they pick up on. Then fix those things and post it here.

I do use Grammarly. Were there any mistakes it missed?

This is way too long for one sentence! Figure out a way to intelligently divide it so that it'll make sense for your readers and you don't lose any ideas.

Sectionalism, slavery, and states rights as the causes of the civil war were all connected because the south practiced sectionalism because they were more concerned with keeping slavery (even to the point of secession, which they claimed was a state right) than with the well being of the other sections of the country or the country as a whole.

Also too long for one sentence:
The southern response to the 1860 election results demonstrates this connection because the south seceded because they were afraid that the north would outlaw slavery(and thus practice sectionalism), so they took advantage of their "states right" and seceded.

Capitalization is needed:
North
South
Southern

http://guidetogrammar.org/grammar/capitals.htm
Read through section 4 here.

The connection between sectionalism, slavery, and states' rights as causes of the Civil War can be summarized as follows: The Southern states practiced sectionalism, prioritizing the preservation of slavery even to the extent of secession, which they argued was a state's right. On the other hand, the Northern states also engaged in sectionalism by refusing to compromise with the South following the Kansas-Nebraska Act, disagreeing with their stance on slavery and rejecting the notion of secession as a state's right. The Southern response to the 1860 election results highlights this connection as they seceded out of fear that the North would abolish slavery, thereby asserting their state's rights when they perceived sectionalism taking place.