As far as I know the Dragons on Earth map is just an extra campaign map based on Earth (practically I don't know if the smallest countries could be individually represented, since there needs to be enough room on the map to show units and buildings, as well as gold/research/population).
I assume it'll look something like a modern version of the "Risk" board game, with smaller countries amalgamated into regions and geographically large countries split up into multiple sections.
