Dutchjet, MIA-EZE is an important route for AA, with two daily 777-200ERs flying it. It's not going anywhere. In fact, AA operated a third-daily special flight with the annoucement of AR's suspension of services, and, if they can get the rights, AA will have zero problem filling up a third daily MIA-EZE flight (UA also has daily 777-200). ATL will never, ever replace MIA as the number one gateway to North America (or JFK as #2). However, ATL provides MUCH, MUCH better domestic connections that MIA will never offer (more for reasons of geography than anything else). But the truth is, however, that:
1) Most Latin Americans final destination in the US is usually New York City or Miami and...
2)...those who don't end their trip there usually continue on to other major American cities, for which Miami provides more than adequate connections (SFO, LAX, SEA, STL, DTW, ORD, MSY, DFW, IAH, MCO, DCA, IAD, DEN etc.)
I am sure DL will find succes flying to SCL, EZE, LIM, etc. from ATL (in fact, they have, AFAIK), but if they ever try doing flights to places like CLO, BAQ, LPB, VVI, GYE, etc., they are going to have trouble filling up planes like AA does out of MIA. Connections to Europe are, for the most part, better from ATL, but, again, MIA has the major connections, not to mention LHR. AA has big plans for MIA when their new terminal opens and plans to make it thier true international hub (currently dailies to LHR, MAD, CDG, codeshares to ZRH, IST), and not just to Latin America. The biggest advantage AA has however, is that no matter how bad the situation gets in Latin America, AA will ALWAYS have MIA's (and JFK's) O&D traffic to keep thier flights, like their five daily Miami-Caracas flights, afloat. DL cannot say the same for ATL.