also because us farmers are given subsidies to grow the corn   that is then processed into oils and sweeteners....
I feel for ya. there are some salad dressings without them, try the Annie's all natural ones.
fresh-baked goods from a bakery (as opposed to a grocery store) will be less likely to contain these products and you can also ask the bakers what they have that does not contain corn.
corn is apparently one of the most common food allergens (but the symptoms may be subtle in some) and this may also be playing a part in the obesity epidemic in the US...