Two copies of the map. Use masks to cut the map in half showing the one country on one layer and the other country on the other.
Keyframe their position properties to move them apart.
If you don't want 3D then you can draw your mask following the same shape that you posted, then do as suggested, use multiple copies and move them apart or animate the mask path to make the crack open up. If your drawing skills need improvement just import that image and trace the cracks then set a mask path keyframe at about 3 seconds and move the CTI to the first frame and move the mask points together to form to a single line. Adjust the timing and position to get the look you want.
If you want it to have edges, then you have to create artwork with edges or stack copies of your layers on top of each other offsetting each copy by one pixel in the right direction. I would offset in Z using this expression for position in a 3D layer then duplicate the layer until I had enough copies to create the depth needed, then I would add a 3D null, make the null the parent of the copied layers, then rotate the null 90º in X to lay the layer down and precompose the entire group and enable collapse transformations.
Oops... here's the expression:
[value, value, value+index]