new comp and add the custom particle layer (tomato) and emitter layer (country).
make the country layer a 3d layer.
add a new solid and add particular. set emitter type to 'custom' and then select the country layer emitter layer and you'll probably want the velocity set to zero. also set the particle type to 'custom' and choose the tomato layer as the particle layer.
if you ram preview at this point you should get tomatoes popping up all over the coutnry. you'll probably want to tweak the particles/sec and the size and life span of the particles (for starters).