Here, on the left, is the Revis family (USA) who spend $341.98/week on food. On the right is the Aboubakar family (Chad) who spend $1.23/week on food. These are two extremes of the spectrum. It's interesting, though to also look at not just what the families spend, but what kind of food they eat. It is not just the Americans eating the processed foods.
The email only had a handful of the thirty families Menzel profiled in the book. Each is fascinating both for what they ate, and what they did not eat. Take a close look at the photos. Many of the other families in the book, "rich" and "poor" drank soda and ate packaged foods. Here are a few more, from kindo.com.