American traveling SEA-SZX-XMN-ICN

Hi, I am an American passport holder traveling from Seattle, WA to Seoul via Shenzhen and Xiamen on Xiamen Airlines. I don't have any kind of Chinese visa. I will be in SZX airport on a layover from 6pm to 8:25pm then in XMN from 9:30pm to 3:50 pm the next day when my flight leaves for Seoul. I was hoping to leave the airport in Xiamen so I can sleep comfortably, would this be allowed on the 24-hour direct transit?