This sounds great in principal, and ending American and European food subsidies would be great for Africa. Additionally, food subsidies distort the market by, for example, making corn syrup cheaper than sugar in the US.

The problem is that many Americans (I don't know as much about Europe) aren't actually that wealthy. Without food subsidies, our food quality would probably increase, but so would our costs. Poor Americans are overweight today because the distorted food costs make it cheaper to eat processed food (that is more expensive to make overall) than to eat basic fruits and veggies and grains. Without subsidies, they would be starving, or at least calorie deficient.

Nixon put in our current system of subsidies because "food should never be an issue in a presidential race". And since then, it hasn't. America may be wealthy, but the wealth is very unevenly distributed. Without social programs, many of our people would be starving as well.