As some countries are much smaller than others and will probably be about the same size as the hanging bulb itself, I experimented with making the boarders 3D out of folded paper coming off the perspex rather than a painted black outline. This will not only contain and help direct the light to the specific country but also keep the cable hanging straight and in place through the whole in the card.
Below are some photos of a test I did with a circle, just to see how the light looked against a white and black wall.

Against a black wall







Against a white wall

I prefer the white wall as you are able to see the overflowing of the light but there is still a highly concentrated area and the white paper illuminates to highlight the boarder.