Do we need a visa? we are US and Canadian passport holders.

We are flying from Siem Reap to Guangzou arriving at 2330. we have a flight at 0900 from Guangzhou to Shanghai. we then have a flight from Shanghai to Detroit Michigan at 1630.
we aren't in China for even 24 hours. can we leave the airport In Guangzhou to sleep in a hotel (Pullman Hotel right at the airport) or do we have e to spend the night in the secure area of the airport? we have tickets and will have boarding passes right through to the US.