All US Nationals need a visa to Visit China. US nationals can however travel visa free to Hong Kong and Macao for a period of less than 90 days.
If you wish to visit Mainland China along with say Hong Kong; you MUST obtain a Chinese Visa before entry into China.
Main types of Chinese Visas are as follows:
Tourist Visa- (L Visa)
Business Visa- (M Visa)
Family Reunion Visa- (Q1/Q2 Visa)
Transit- A foreign citizen transiting through China by Air is exempted from a Visa if he/she will stay only in the airport for no more than 24 hours and has a valid connecting flight with confirmed seating on an international flight.
Citizens of Singapore, Brunei and Japan with an Ordinary passport are exempted from a Visa if he/she visits mainland China for tourism, business or meetings with friends or relatives for a period of less than 15 days.
Duration of a China Visa varies from as less as a Single Entry 3 month Visa to a Multiple entry 10 year Visa; with a maximum of a 2 month stay in one trip on a 10 year visa.
Regular Processing time for a Chinese Visa is 4 business days, and for a express service is 2-3 business days. Processing times may vary depending on a case to case basis and on the discretion of the embassy/consulate officials.