Kraft singles are still cheese. They've just been pasteurized and adulterated with sodium citrate.

No, if it was just cheese that's been pasteurized and adulterated with sodium citrate it would be pasteurized process cheese. A couple other additional additives are acceptable.

When it has other additives but is at least half cheese by weight it's pasteurized process cheese food.

When it's pasteurized process cheese product it's not meeting any of those standards. Often because it's less than half cheese or an addictive outside the accepted list to meet the other definitions is being used. Milk protein concentrate is an example, but also increasing the fat content with something like vegetable oil or adding flavoring agents to make the result taste more like cheese.

The FDA caught Kraft singles not meeting the definition of pasteurized process cheese food something like 20 years ago which is why it's labeled a pasteurized process cheese product.

For any curious, the sodium citrate is an emulsifying agents that helps the natural cheeses used melt together smoothly, and pasteurization was originally done to prolong the life of the resultant mixed cheese as the whole original point of American cheese was to reprocess ends and scraps into something homogeneous and comparatively safe for long distance overland transport before refrigerated trucks were a thing.