The advisory also warns about China's use of "exit bans" that would prohibit US citizens from leaving the country, sometimes keeping them in China for years.
Reports say the travel guidance issued by the United States comes after the detentions of two Canadians in China last month and came amid heightened diplomatic tensions in the wake of the arrest in Canada of a top executive in Chinese telecoms giant Huawei.
Under Chinese criminal procedure law, special forms of detention and interrogation can be used for state security suspects.
There are approximately 200 Canadians overall who have been detained in China for a variety of alleged infractions and continue to face ongoing legal proceedings, and the number has remained relatively stable in recent years.
China has detained 11 Canadians since early December when a senior executive of Chinese telecom giant Huawei was arrested in Vancouver on a United States request for alleged violations of Washington's sanctions on Iran, according to Ottawa.
"Without a doubt, these two Canadian citizens in China violated our country's laws and regulations, and are now undergoing investigation according to procedure", Zhang Jun, China's prosecutor general, said. He said, "It is not convenient to disclose more information now".
December 7: Foreign Affairs Minister Chrystia Freeland says Canada's envoy to China has briefed Chinese officials about Meng's case.
After news broke of Kovrig and Spavor, Minister of Tourism Melanie Joly postponed a planned trip to China to attend a tourism event at the last minute.More news: Tokyo: Nine Injured After Car Rams Pedestrians in 'Terror Attack'
The Chinese government has only given vague details about the detention of the two Canadians, and it has not drawn a direct link to Meng's arrest.
Zhang said the investigation process had been handled "strictly" according to law when asked by Reuters at a briefing when the two men might be charged. The move also comes amidst the arrest of the CFO of Huawei in Canada, who now faces extradition to the USA amid fraud charges.
Later in the day, Meng is released on $10 million bail.
December 14: Canadian officials are granted consular access to Kovrig, and McCallum meets with him in Beijing.
"This doesn't shed much light", said Malley.
In comparison, there are nearly 900 Canadians in a similar situation in the United States, the official added.
Canada has sought the support of key allies in pressuring China to release Kovrig and Spavor.
Malley said he won't speculate on why Kovrig was detained, only to say it has nothing to do with his work as an analyst for the Crisis Group.