@LDF its not big of a map as one would expect seeing it depicts all the world. but all in all it has like 20 big cities. so 20x the gta san andrease size.
if there are lots of people with free time or a motivation of money etc. this is possible yes not impossible at all. for a mod.
game studios would rather invest in something realistic as this is too small even if u put country of united states in perspective.