If you fly on Delta for your domestic segment, you will be able to reclaim your baggage at customs in ATL, and then after you exit the customs hall (but before security and baggage recheck), there is a Delta desk where you can check in for your next flight and have your bags tagged for your domestic connection. I've done 1 hour international to domestic connections in ATL, but I would strongly suggest at least 1.5 hours if not 2 hours.