One of the difficulties of Africa is the weather and environment.
They have poor weather which they cant harvest plants to produce and distribute to the world. Which make them poor and not able to have material for a modern economy. And they dont have any resources to again produce to other countries.
The main reason why the United States remained out of World War II prior to the Japanese attack on Pearl Harbor was because there was a very strong isolationist sentiment in the United States that had existed every since World War I.
New England had small farms most likely used for familys and the southern farms were big and they made a lot of money. the south also had better soil than the north