American cheese availability and utility
American cheese isn't real cheese, but a processed cheese product made partially from cheese, but with loads of extra stuff added in to make it pliable and melt easily. The "American Cheese" you see in the ingredients is the real cheese part of it, although the American part of it is probably for marketing purposes. 

It's not a substitute for cheddar or other cheese from a flavor, texture, or melting point perspective, although it can be used in many of the same things. If you want a cheese that tastes good then use real cheese, if you want something that looks and tastes a bit like cheese and melts quickly and evenly use american cheese.