JFK-MEX, JFK-PHX, and LAX-GRU would do fine loadwise, but I don't think AA would have a hit.
MIA-MAO would do very well with a 738. AA applied for this route in 1998 and intended to start service that fall, but it never surfaced.
ORD-WAW would probably do good, but yield may be an issue.
JFK-JNB? No way. Forget it. MIA-CPT-JNB would be a goldmine considering Miami has America's largest South African community. AA was looking into doing MIA-CPT, 3x weekly with 777s back in 2000, but their 777s do not have the range to make the flight economical.