IS there an easy way to find the city that has the lowest fare from an international destination.

Example on AA I have found- GIG-AUS could be $1500 RT, while GIG-LAX could be $900.

It might worth flying GIG-LAX then use miles or a cheap flight to/from AUS.

Is there any tool that can do this short of inputting in a whole bunch of cities? AGAIN- just looking for the cheapest U.S. destination city, I can figure out how to get from there to AUS.

THANKS