Timatic suggests that you can get a 24-hour transit including leaving the airport simply by presenting onward tickets at CAN.
http://www.staralliance.com/en/servi...sa-and-health/ is one of many places that the information can be found online.
National U.S.A. (US) /Embarkation Thailand (TH)
Transit China (People's Rep.) (CN)
Destination U.S.A. (US)
ALSO CHECK DESTINATION INFORMATION BELOW
China (People's Rep.) (CN)
TWOV (Transit Without Visa):
- All transiting passengers are subject to passport control.
For more details on document requirements, please enter
China (People's Rep.) as a destination.
Visa required, except for Those passengers continuing their
journey within 24 hours (or within the same day at Guangzhou -
CAN) to a third country by the same or first connecting
aircraft, and holding documents and confirmed tickets for
their onward journey. Leaving the airport transit area is
allowed. Overnight facilities are available outside the
airport:
Visa required, except for Nationals of U.S.A., provided
arriving at and departing from Shanghai Hongqiao or Pu Dong
airports only, continuing to a third country within 48 hours
and holding confirmed onward tickets and all documents
required for next destination.
Warning:
- Passengers not complying with the entry or transit
regulations will be deported by same or returning aircraft.
For details, click here
U.S.A. (US)
Passport required.
- Nationals of U.S.A. may enter with a passport and/or
passport replacing documents valid on arrival.
Passport Exemptions:
- Holders of a Temporary or Emergency passports.
- Holders of a Transportation Letter:
VISA NOT REQUIRED.
Minors:
- Children, up to/incl. 15 years of age, being nationals of
U.S.A., are not allowed to enter the U.S.A. on their parents
passports.
CHECK TINEWS/N1 - USA: NATIONALS OF GREECE
Timaticweb Version 1.3
12 March 2010