You’re getting mixed up between the requirements for “American Cheese” and “American Cheese Food,” which are distinct.

“Pasteurized Process American Cheese” is a cheese that follows a government regulatory definition, where the inputs are mostly cheddar and Colby cheese, and the milkfat requirements make it a little more difficult to try to make it with too much non-cheese ingredients.

Kraft Singles are the less strict “Process American Cheese Food” which only has to be 51% cheese by weight. But the labeling makes clear that it’s not just cheese. Kraft Deli Deluxe slices are labeled with the stricter definition of “Process American Cheese,” and pretty much any brand will have to stick with the label requirements.