Velvets has its uses and some may indeed include mixing it with food. But I doubt mcD uses Velveeta. Just a guess whatever they use comes from a plastics factory
The cheese is listed as “pasteurized process American cheese” on the McDonalds website:
https://www.mcdonalds.com/us/en-us/product/cheeseburger.html
So apparently it meets the FDA threshold for being considered actual cheese rather than cheese food or cheese product.
Here are the listed ingredients: Milk, Cream, Water, Sodium Citrate, Cheese Cultures, Salt, Color Added, Sorbic Acid (Preservative), Citric Acid, Lactic Acid, Acetic Acid, Enzymes, Soy Lecithin.
I do wonder what “milk” means here, though. Is it milk milk or is it milk protein solids, the latter being more of a hallmark of less than natural cheesoids.