Sorry, Elvia, but your statement is both true and false. Is some of the cheese and chocolate awful? Sure, if you choose to buy the cheapest stuff, but basically everyone who lives here also has access to the best of the best, as well. That's the cool thing about the US. We have virtually everything here. What one decides to put in their mouth will depend on personal preferences and finances. Availability is rarely an issue.
With that said, each country has certain characteristics which can cause one to make a generalization. For instance, the U.S. has a million fast-food restaurants, so if one comes here and wants to keep their meal cost in the $5-$8 range, that is pretty much what they'll be eating. This has caused some people to not only dislike the food here (based on their own limited experience), but to mischaracterize it as well.
For example, I knew of a Thai girl who came here on a K1 Visa to be with her husband in the U.S. Unfortunately, her ex-military husband was rather poor, living at near poverty level according to the current U.S. poverty guidelines. She went from eating her native food (mostly home-cooked by her family) to subsisting almost entirely on burgers and fries (or variants thereof). After a few days she absolutely hated it and came to the conclusion that she did not like the food in the U.S. Because of her own limited experience, she was unaware of the vast number of dining options available to her. Therefore, she wrongly characterized the U.S as being "all burgers and fries".
Few countries (if any) have as many fast-food restaurants as the U.S., so it is understandable why people might make the above assumption. Still, even with all those fast-food restaurants around, we still have a massive variety food available for anyone who wants it.