I am a U.S. citizen visiting Hong Kong, can I get a Chinese visa to Shenzhen, China in Hong Kong?

Yes, you can get a Chinese visa to Shenzhen in Hong Kong, it is easy for U.S. citizen to get a China visa in Hong Kong. There is a reception desk of CTS Hong Kong in the Hong Kong International Airport, you can entrust it to obtain China visa for you. Or you can submit visa application to Commissioner's Office of China's Foreign Affairs Ministry in Hong Kong