The Civil War was in result of Slavery. The Confederates and The Union fought in order to abolish, or keep slavery in the United States.
Economic and Social: People started the Underground Railroad to get slaves to parts of the country/Canada in order to be free. This is both economical and social because they were a community that helped slaves.
Geographic: It was illegal to own slaves in parts of the country, while others it was legal. The Underground Railroad took place all over the country in both Legal and Illegal states.
Political: People wanted to abolish slavery, while others didn't. This led to war, to settle the conflict. Also, if Slaves were caught in free states, they could be sent back to their owners.
I would focus on how one of the empires lasted for nearly 2 millennia (if you count Byzantium as Rome), and how the other fell apart very soon after the empire’s namesake “Alexander” perished.
