Corrections: There are several mistakes in this article, from plot-related to grammatical. The ones I can think of off the top of my head are: a) Adah's right side, not her left, is crippled, b) the author used "effect" as a verb, and c) it's wringing, not ringing, near the end. Someone should probably look over this sometime. Also, the article presents Nathan Price as a completely flat character; however, he has his moments of uncertainty (for example, when he reshapes his garden into mounds, or when he reacts to the news of the little girl drowning in the Congo River by saying something to the effect of "Why didn't anyone tell me that? That's important!" Also, he was religious before the incident in the war. Why?). Are you sure there's nothing more to this man?
Now, ideas: Did anyone else here see connections to the Bible, specifically the Old Testament? I think that the name "Poisonwood Bible" may be taken literally. As I see it, Congo represents the land of Canaan. The Americans are the Chosen People. Just as the Israelites were provided for in the desert for forty years without having to work, so the Americans are provided for excessively. Just as the Israelites conquered Canaan, renamed it, killed many of the people, and forced their religion and leadership upon it, so the Americans did to Congo. With an ironic twist, Kingsolver presents the Chosen People as the bad guys, directly contradicting the Bible.
On a smaller scale, the village in which the Prices resided for some time can represent Egypt. Geographically, both this village and Egypt are in Africa. Also, the girls are held there unwillingly by an evil master for whom they must work, like the Israelite slaves for Pharaoh. Just like babies were killed in Egypt, so the youngest, Ruth May, was killed here. Finally, later in the novel, when the girls and their mother ask a local market woman about the town (which she should know about as she lives right next to it), she reports that she has never heard of it. Inexplicably, the town has been destroyed beyond remembrance - just as the Egyptian civilization was completely destroyed after the Israelites left it.
Well, those are my theories. That was longer than I'd thought it would be . Sorry!