on the way to and from thailand i have a layover in shanghai do i need a visa to leave the airport?

I have a u.s. passport and living in korea
i plan to go to thailand through the week of 24-31
on the way to thailand, and on the way from thailand i have 1 day layover in shanghai
Chinese Embassy website says if i have a visa of the country I'm going to (thailand) i don't need to get a chinese visa
however
thailand doesn't require a visa for u.s. passport cardholders
do i need a visa for 2 stays of 20 hours in shanghai