I have an award ticket to Asia for October: SFO-SGN on CX, then SGN-PVG-NRT-SFO on JAL.
I arrive PVG via NRT from SGN at 12pm on Monday, then leave PVG to NRT at 11:50am on Wednesday. With a US passport and ticket receipt, is it ok for me to leave Pudong Airport to go to the Expo without a Chinese visa?