Maybe this hack could help you:

http://processing.org/hacks/doku.php?id=hacks:using-awt-s-polygon-class-to-test-for-insideness

I made this using an image that was in data folder but was never displayed.
It works fine.
it can be seen at:
www.kubrusly.com/vicente/genius/
(click in the applet then any key starts or restarts the game)

The part of the code that uses this is;

PImage mapa; //<- never called for display.

//folowing is a method inside de sketch

int jog(){
 color cor= color(255);
 cor = mapa.get(mouseX,mouseY);  // mapa is a gray scale version of buttons
 int cori = int( cor >> 16 & 0xFF);   //<- bitwise "get red"

 switch (cori){
 case 30 :
   return 1;  
 case 70 :
   return 2;
 case 110 :
   return 3;
 case 150 :
   return 4;                
 default :
   return 8;
 }
}

The 2 images can be seen at :
www.kubrusly.com/vicente/genius/image_map.html

devlar
I'm not a very experienced user, but i think that you want may be done in a simple way:
get your map in an image application.
make each region (countries or whatever) one single different color( i used different grays) the map and the graymouseovermap must be coincident.
define both as PImages.
load the map to display
test mouse position in graymouseovermap to see witch color is under the pointer.
That's it
I made this fast example for you. Note that mine gray map is not good (jpeg created different grays than i want) but is just a quick for instance.
The number at the bottom is the brightness value of under mouse region.
You can be much more precise, again it's a quick&dirt for instance.
I hope it helps
www.kubrusly.com/vicente/mapa/

the images used are at:
www.kubrusly.com/vicente/mapa/mapas.htm