Since your flight goes Beijing-Seattle-Atlanta-Nashville, your international arrival city is Seattle. At SEA you will have to go through immigration, reclaim your bags and go through customs, before rechecking your bags to your final destination.

That would be the time to ask/ request the DL Agent at SEA to check your bags only to ATL, and not to BNA.
Guess if you explain why you need to stay an extra day at ATL ...since you recently found out that you have an important meeting in Atlanta the day after I am flying through.

You would still need another flight to Nashville after my meeting. Otherwise be prepared to pay change fees + fare differences.

If it was me, I would go home to BNA, and get a separate round trip flight BNA-ATL-BNA the day after, instead of going through all this, on the way back from an international trip. But that is me!