A friend's wife is from Kenya (Kikuyu). The quality of her English grammar is better than that of most Americans these days. I'd be more surprised if it weren't perfect.
By the way, as another data point, Obama's school registration from Fransiskus Assisi school in Jakarta (here), likely filled out with information provided by Lolo Soetoro, says he was born in Honolulu (see line 2). While it's possible Obama's mother lied to her second husband, I think we need to be very careful that people here aren't making the same mistake Dan Rather made, trusting a document because it say what they want it to say.
I recently watched the documentary about the modern day explorers retracing Stanley’s search to find Livingston. The Maisai spoke the most perfect English I’ve ever heard