American cheese availability and utility According to Wikipedia, the product commonly (and in that article) called "American cheese" is


  generally manufactured from ingredients such as one or more cheeses, milk, whey, milkfat, milk protein concentrate, whey protein concentrate, saturated oil(s), emulsifiers, and salt.&hellip; American cheese can not be legally sold under the name (authentic) "cheese" in the US. Instead,&hellip; laws mandate that it be labeled as "processed cheese"&hellip; or "cheese food"&hellip;. As a result, sometimes even the word "cheese" is absent, altogether, from the product's labeling in favor of, e.g., "American slices" or "American singles".


It seems from Wikipedia that there is no actual cheese that may be labeled "American cheese". Yet, the product in my refrigerator labeled "white American pasteurized process cheese" has as its first ingredient "American cheese". Specifically, its ingredients are:


  American cheese (pasteurized milk, cheese culture, salt, enzymes), water, cream, sodium citrate, salt, sorbic acid (preservative), olive oil.


What is that "American cheese" the label refers to? Is it available on the market? Can I use it in substitution for, perhaps, American slices, or maybe instead of Cheddar or something?
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.