China has in the past 10 years become the dominant trading partner for Africa, displacing mostly western economies as the top importer in many countries, notably Nigeria, Egypt and South Africa. These two maps show the change pretty clearly.
The data is drawn from MIT's Observatory of Economic Complexity. The first map shows African countries' top importers in 2003. European importers (mostly France) are purple, African importers are light orange, India is dark green, the Middle East is light green, China is red, and the United States is blue.
And this map shows how the landscape has changed. Same color code. You'll notice blue is gone, and purple is on its way out. China is of course ascendant, but more African countries are importing to other African countries as well.
U.S. companies still do a lot of business in Africa and hope to do more, but America is no longer the top importer in any African country.
(This has been reposted from a September 2014 item on 3D Economics, which is being phased out.)