Why are certain bread products developed in certain countries?

Answer 1

The basis for all breads is grain. The grain is milled into some form of meal or flour to be baked into the local bread. Bread recipes were developed using easily available local ingredients. In many countries that grain is wheat. Depending on how fine the local milling process was the flour could be very coarse making a heavy (dense) product.

Before ovens were common "bread" was really just a mixture of meal and a little water and oil and cooked on hot stones making more of a flatbread or unleavened cracker type cake. Many nomadic cultures developed this and it still used around the world.