that's the power of huge agricultural conglomerates in the US at work. they find very creative uses for corn and soy products, both of which are grown in excessive quantities here. in some cases, they manage to pass legislation mandating their use (such as ethanol additives in gasoline, here in the midwest).

I'd heard it was more due to sugar lobbyists than corn lobbyists: that the price of sugar is kept so (artificially) high in the US that it's cheaper to use the corn stuff. In England and Mexico, by contrast, the most economic thing to do if you want sugar is to use sugar.

Another one (which I can't dig up a link for at the moment) is the power of rice lobbyists: rice is apparently viewed as a "strategic" crop in the US, so its production is governmentally propped-up, even to the extent that knee-deep paddy-fields in desert states are eyed enviously by citizens of towns with water shortages.

Peter

Edit: Not, of course, that the EU's Common Agricultural Policy is any saner.