US Chinese food vs Real Chinese food

I've hear people that were born in China and come to the US to try our Chinese restaurants say that they're very different compared to the food that's actually served in China. 

Can someone explain the differences in our perception of Chinese food and what's actually over there?

When I think Chinese food, I've been brainwashed into thinking of "Mandarin Chinese" food, which is basically fast-food Chinese. Chicken fingers, beef teriyaki (lol teriyaki is not chinese, but whatever, americans think all orientals are the same anyway), boneless spareribs, pork flied lice, etc

Hilariously (sadly) enough, things like Boneless Spareribs are covered with what really amounts to Ah-So sauce, and Ah-So is a stereotypical saying that wartime Americans attributed to Japanese.