I'm US citizen, transit through Shangai Pudong twice in one week, will I have problem?

I am a US Citizen on vacation flying from Hong Kong to Japan via Shanghai Pudong Airport. The first flight has an overnight layover in Shanghai of about 19 hours total, which I would like to stay in a hotel in central Shanghai and do some sightseeing before boarding the flight to Japan. Then two days later, I fly from Japan to Hong Kong through Pudong where I will stay in the terminal due to a short 2.5 hour connection time between flights. Will I encounter problems in Shanghai, especially on my way back to Hong Kong, since I was there two days prior?