What was the main reason many Southern states
chose to seceed from the Union?

Slavery

Explanation:

The direct cause was Abraham Lincoln, a Republican president being elected, which caused South Carolina to secede and the rest of the southern states followed. The long term reasons were of course the issue of slavery. The southern states wanted to transport their slaves anywhere in the country, and felt that their interests would be threatened if Abe Lincoln was elected.

byzantine empire is the answer i think you are looking for.

hope this : )

popular sovereignty   influenced the declaration of independence because the colonists wanted to have freedom to do they wanted so they put into writing