USA passport, direct flight from Tokyo-Shanghai then Shanghai-Chicago with 18 hour layover

Based on recent reports, you only have a shot if a) your flight leaves on the next calendar day or you are going to a different airport, and b) you have a hotel reservation if staying overnight. Keep in mind that even if you have all the required documents, the immigration officer handling your case may still not allow you to enter the country since you are not holding a visa.