Probably in the same way that one could explain how the existence of Taco Bell does not preclude racism towards Mexicans.
American Chinese food is a lot sweeter, thicker, and more soy sauce based.
Your equivalent statement about Mexican food would be that you assume Taco Bell is what most Americans are eating as Mexican food. That doesn’t seem a valid assumption at all - maybe for a certain demographic (e.g. young) that’s true, but I’m very skeptical that such a claim would stand up to scrutiny.
Similarly, you cannot group the corner store (nominally) Chinese restaurant owned by a Chinese (or as likely in much of US, Korean) family as being in the class of highly processed, pre-made food as Taco Bell. Sorry but no.