[Butch Cassidy Slept Here]

If there were two sets of tickets--1. (unknown domestic city) to Miami (round-trip), and, 2. Miami to Santiago (round-trip) then only the return flight from Miami would be cancelled. The remaining reservation would stay intact.

I'll give the OP the benefit of the doubt and assume she was referring to train travel between her home town airport and Miami, and not on the mythical Pan American Railway.

This is, yet, another example of what happens when you rely on miles, rather than cash, for air travel.