African and American - conflicting elements in All Their Names

Started Dinaw Mengestu's All Our Names and it immediately felt familiar: it had been a New Yorker fiction selection some months ago; actually, the New Yorker excerpt, about a young man from the country in or near Uganda goes to the capital, becomes a hanger-on at the university, links up with some fellow student radicals, in particular a charismatic young man named Isaac, and gets involved in a campus demonstration that ends violently, and then flees, is half of the first section of the novel, a section that proceeds in alternate chapters named for their narrators, Isaac and Helen. The Isaac chapters take place at the university in Uganda, and much of the focus is the extreme class divisions in the country, in the continent, then and probably now - these scenes seem to be set in the late 60s or early 70, in the era of dreams of a pan-African culture and the beginnings of independence and extreme corruption (Achebe has written well about this era as well); the Helen chapters are narrated by a social-services worker in a Southern university town who takes on the case of a newly arrived African exile, Isaac (we know that he is the narrator of the first section as well, and that he has appropriated the name of his radical and ill-fated companion). The African chapters are by far the better, really conveying the feeling of the university and the nation in its nascent state and full of turmoil and danger. The American chapters, by contrast, feel somehow generic: for example, Helen makes it clear that this is a Southern town only recently integrated, and in the best scene in these chapters the staff at diner essentially refuse to serve Isaac - whether because he's black or because he's with a white woman is not clear and doesn't need to be clear - but there are no surface or topical details that tell us anything about the town itself, we have no sense of the space or the place. In fact, we have no sense of Helen; she pretty quickly becomes sexually involved with Isaac. What does that mean to her? Obviously, she is breaking through a cultural taboo, but she hardly reflects on that - what it's like for her to be with an African man, how that separates her from family and friends. In fact, the more troubling aspect is her almost immediate involvement with one of her clients - but she has no reflections on that, either. As the entire first section of the book is set in the late 60s-early 70s, I'm guessing that later chapters will come close to the present and may follow the lives of the descendents of Isaac and Helen - people much like Mengestu himself, perhaps.