When I had trouble doing TWOV on MSP-NRT-PVG-DTW-MSP, the very senior supervisor got a CBP agent looking for excess cash in the jetway to agree with her that you cannot go to China without a visa. The next authoritative source was the USA State Department website [can you imagine trying to tell someone that information published by the Chinese government is a good source for whether a Chinese citizen can enter the USA?] which seemed at say that for TWOV you must have a visa for your next country. In particular, since the USA will not issue a visa for a USA citizen, no USA citizen could ever do TWOV on USA-AAA-China-USA, nor could you do USA-China-BBB-USA for any country BBB that doesn't require visas for USA citizens, so traveling back through Japan, South Korea, Taiwan, Singapore, etc. would all be excluded.

On an earlier trip, I was eventually able to prevail (after hours of arguing at NRT) on USA-NRT (about 50 hours)-China- USA. Boarding flights to leave the USA was no problem, but OLCI in Tokyo said that a visa was required, so I went to the airport about four hours early for confirmed business class with no bags to check. I was finally cleared to board just as boarding was starting. Along the way, I had four check in agents and a supervisor doing crazy things like calling random friends in China who believed that everyone going to China needs a visa. I finally convinced a higher level supervisor in the lounge, based on websites of some organizations that were promoting TWOV tours to China that were specifically routed with a connection through a third country in one direction.

Throughout, they were convinced that I would be unable to leave the airport and came very close to insisting that I make a reservation (which would have been nonrefundable at that time) in a PVG airport hotel. I knew that all PVG airport hotels were landslide but omitted telling her just in case I had ended up needing to do this. Note that if for some reason I want to spend two days sleeping on an airport floor, it is not the airline's business.