What was the border between slave and free territories west of the mississippi?

For in this unit, you read about transitions of power and the formation of newly independent nations in africa, asia, the americas, and the middle east. some of these transitions were peaceful, while others caused long-term instability. why do you think some countries were more successful than others with political transitions? what do you think were the biggest challenges facing newly independent countries? would it have been possible for leaders to prevent these problems before they happened? why or why not?