Christian fundamentalists created cereal ?. No they didn't. Kellog turned a cereal ,maize, into a breakfast food. totally different thing.
Most of the breakfast cereals are so poor nutritionally that they have to be boosted by adding vitamins.
Many American cultural ideas comes across the Atlantic and our supermarket shelves are laden with dozens of nutritionally poor sugar laden foods that can only be sold by having a massive advertising budget.
I ,as did most of my peers grew up eating .porridge for breakfast. Simply oatmeal,water and a little salt.
Cheap and nutritious and it doesn't make a huge profit for multinational companies like Nestle.