Stopped over in Pu Dong, Shanghai, from Cambodia to NY, USA

I am holding US passport and I will layover 6 hours in Pu Dong, Shanghai, on my trip back from Cambodia to US. My wife and 2 children are also hodling US passports. Are we eligible for 72 hours free transit? I know that people must also ask same question, but I do wish to hear directly from people who know the issue.
Thank,

Chhan D. Touch