It would make Africa less corrupt and it would give the US access to Africa's resources. It also would help lift Africans out of poverty since the US would make infrastructure on the continent. Plus, China is doing a lot of investment within the continent. A US invasion could help spur US influence.
@asta, A land invasion of the continent of Africa spurring US influence. I don't think the world will react to the US TAKING OVER A CONTINENT the way you think they will. I also don't think an invasion of an almost 12 million square mile landmass and the suppression of a population of about 1. 2 billion spread out over the savannahs, The second largest rainforest in the world, And the largest desert in the world would go the way you think it will.