If someone wanted to make the argument that a dish was not authentic, one would argue that certain dishes like General Zhao's were nothing like dishes in China. I hear that it's like Sesame Chicken and like General Tso's Chicken, and that these dishes along with Chop Suey aren't a normal part of food in China but are basically part of American dishes that Chinese or Chinese-heritage people made in the US. I heard that General Tso's Chicken is part of Taiwanese food since a chef invented it in the 1950's, but am not sure how common it is there. Supposedly this chef later brought the dish to NYC in the 1970's.In terms of Panda Express - I have had much better Orange Chicken - but for whatever reason, the Chinese students I come into contact with all are very curious about this dish - that and Genera Zao's Chicken. Apparently there is nothing like it in China.
I'm no specialist, and Chinese cuisine is varied in China with so many regions, that I can't really answer that. I don't know how much of Chinese-American dishes match dishes in China, and how close the resemblance is.
Imagine that I opened a "fajita" shop in Ukraine and made my fajitas with parsley, pita shells, Italian marinara, and Italian meatball beef instead of normal fajita ingredients. Imagine that it caught on in Ukraine but not back in the Americas. This would seem like a good analogy of the problem. Someone could argue over whether my product was authentic Tex-Mex or not.