There are all kinds of American restaurants in China. Some are good, some are completely horrible. Some are authentic, some are stereotypical cartoons of American culture.
In big cities like Shanghai and Beijing, you'll see authentic American restaurants, owned and operated by Americans, serving the people they came from. For example, on a couple of occasions I've been to Texas restaurants in Beijing owned by Texans who serve chili, tacos, burritos, burgers, steaks, onion rings and other Texan food like you'd get in Texas.
However, other restaurants can be very unpopular, even in big cities. Often, instead of boasting that they are American, they will have a sign that says Western food. Now with that title, you might think you can get some French or Spanish dishes, but one look at the menu and you'll realize it's just American cooking, usually a variation of American cooking.
You'll usually find some salads, sandwiches, steaks, hamburgers, pizza, pasta and shrimp. Of these, salads are probably the safest choice. The others may disappoint you.
The steak will likely be overcooked, crispy, and drizzled with black pepper sauce. The pizza will be soggy. It will have too much cheese and toppings in it, and every little tomato. If there are tomatoes, it's probably tomato sauce. Canned fruit is often put on pizza. Spaghetti is pasta topped with tomato sauce. The meat in the sauce is the same as the meat on the pizza.
But once in a while, you'll find a nice restaurant. It's just that sometimes, you find a restaurant that actually cooks its steaks medium rare, makes its pasta with real tomatoes, and knows how to bake a real pizza with the right toppings.
Of course, you can play it safe and go to a big brand fast food chain. There are KFCs everywhere, and in most cities you can find McDonald's, Starbucks, Burger King and Pizza Hut.
Here are some pictures of burgers and other western food I encountered in China.
Burger, onion rings and pizza in the back.
Fish and chips with mayonnaise and ketchup. Burger and fries. Burger with an egg, luncheon meat, bacon and slaw. A chicken burger, similar to KFC's, but much larger. Pork burger with fries, slaw, ketchup and honey mustard. Baked spaghetti with meatballs. Sausage, bacon, luncheon meat and slaw topped on a burger bun, drizzled with honey mustard sauce.