I think you're generalizing too much, JBI. Americans aren't necessarily readers of bad books and Canadians readers of highly literary books. There are readers of good and bad books in each country and good and bad authors from each country. For example, I read a book by Anne-Marie MacDonald, a Canadian, and it was terrible! She might be okay as a poet, but she's a terrible novelist. Yet Canadians read her.
I really don't know any American who runs out to buy a book just because it has an Oprah sticker. The Oprah sticker is transparent to me. If the book's bad, I'm not going to read it, period. If it's good, the Oprah sticker doesn't bother me in the slightest. And I never pay any attention to who wins the Pulitzer, but I do care who wins the Booker. Most American readers I know don't care a bit about the Pulitzer. We know it's given to something "popular" or "trendy" at the time rather than something truly good. I'm always curious about who wins the Nobel, but I don't put much stock in it. For example, there's no way Orhan Pamuk deserved to win. He won for political reasons.
Toni Morrison is an American who writes bestselling books and they are among the best written in the world. Some people may not like them, but they are masterpieces. If a book is a bestseller, naturally the publisher is going to proclaim it as such, bad book or good.
American writers are such a mixed bag or literary and commercial because there are so many more American writers than in any other country. We have some of the best, e.g., Morrison, and some of the worse, e.g., Dan Brown.
Now, if we want to talk about the truly elite readers of literary books, we have to talk about the French, the Germans, the Italians. Continental Europe. For my money, the most literary writers are the Irish - then and now - and some of the Eastern Europeans, the Czech and the Polish, especially.
P.S. I read "The Kite Runner" hoping for a good book, but I thought it was dreadful, just dreadful writing. However, in all fairness, Khaled Hosseini did return to Afghanistan in September 2007 as good will envoy for the U.N. High Commissioner for Refugees. Probably a "publicity return," but I can't judge his motives. That would not be right. I'm no mind reader.