Will I need to re-check my bags at ATL before my international connection?

When you check in with Delta at DFW, they will check your bags all the way to EZE if you purchased your trip on one ticket i.e. DFW ATL EZE ATL DFW. If you purchased a separate ticket for the ATL-EZE segment, then you will need to let the agent know at DFW that you have a separate ticket for your international flight and show them your itinerary for the second ticket so they can check your bags all the way through to your destination.