What exactly does "real American Cheese" consist of?
It's "processed cheese food" and not cheese at all.
Not true. Real American cheese is a “natural” cheese as referred to in the following excerpt. It is a very mild cheddar cheese. Processed cheese food iis franken cheese:
Processed Cheese: What is that Stuff Anyway?
Zey Ustunol
Dept. of Food Science and Human Nutrition
Processed cheese is made from natural cheeses that may vary in degree of sharpness of flavor. Natural cheeses are shredded and heated to a molten mass. The molten mass of protein, water and oil is emulsified during heating with suitable emulsifying salts to produce a stable oil-in-water emulsion. Depending on the desired end use, the melted mixture is then
reformed and packaged into blocks, or as slices, or into tubs or jars. Processed cheeses typically cost less than natural cheeses; they have longer shelf-life, and provide for unlimited variety of products.