Your card is now widely used in major city in China. but still, not all the place accept credit card such as gas station, small store, small resturaunt. but US card can be use at all ATM machines
good for you

You can withdraw local currency from the ATMs with your credit card as long as the symbols and logos of your credit card are shown on the ATMs. The ATMs are very common in large cities. It should be noted that different banks have different limits on the sum that can be withdrawn each time from the ATM, with most permitting a withdrawal of 20,000 Yuan in any day. Since the exchange rate will be converted automatically within the ATM working system, a certain amount of handling charge will be added to the cost.

Also you may exchange your currency and traveler's check at the banks, banks' cash centers at major airports and hotels. Credit cards can be used for shopping, dining and other transactions in most major Chinese cities, such as Beijing, Xian and Shanghai, but generally unacceptable in rural out-of-the-way areas and some small stores. Cash is more popular in China than in many Western countries, so it is important to carry enough cash and change at all times for your petty expenditure.