Quoting Cubsrule (Reply 20): IAH is not a good hub for Latin America. It is a great hub (probably the best hub) for Mexico and not a terrible hub for Central America. For the Caribbean and South America, however, it's no good for anyone east of the Mississippi. |

Quoting RyanairGuru (Reply 29): ATL, while in a superior location compared to IAH for North East-Deep Latam connections, serves a tiny O&D base and relies on connections, which aren't necessarily particularly high yielding. ATL is a stronger market than CLT, but Atlanta ain't no Miami. |

UA and DL will never be able to match the efficient coverage of both Latin and deep South America like AA with their double-barreled combination of MIA and DFW.
The silver lining for UA and *A is that they have an ace-in-the-hole with CM and PTY. For the markets in the eastern third of the U.S., PTY could offer an excellent alternative to MIA as a connecting point to the Deep South and secondary cities in the region that cannot sustain wide-body/long-haul service from the U.S. CM, with their narrow-body fleet and extensive route map in the region, can fill almost any gap in the UA/*A system that UA can't feasibly do from IAH.
http://www.gcmap.com/mapui?P=bos-pty...a-pty,+pty-bsb,+IAH,+LIM,+EZE,+SCL
[Edited 2014-08-20 05:12:15]