MIA-GRU 7.5-8 HRS, MIA-SCL 8 HRS, MIA-EZE 8.5-9HRS. LAX would make for a really long flight, pretty sure you could tag 4 hours onto those flights. Delta services those city pairings out of ATL. Lan offers direct flights from JFK to eze and scl all direct flights. The flight time/market is probably why you can not find the flight you desire. Miami and NYC both have large S.A. markets, Atlanta is just Delta's hub.