Although the picture doesn't as much mock the nations as the many lame stereotypes existing about them. though in Japan's case, one could almost take it for a compliment... although I can't tell if the Japanese themselves would... Well, at least thank God the artist had Gundam hanging in his mind instead of, say, Akira or Evangelion
That's a Zerg Hydralisk. A unit in the Starcraft universe. It's a very popular "pro-level" RTS game that the Koreans excel at internationally. It is also known that the majority of the market share of the Starcraft franchise was contributed by the South Koreans (around 45% ish?). It got so popular, even their national carrier ran a series of ads to celebrate the (recent) launch of StarCraft 2.
EDIT/ADD:
My interpretation of the picture....
Europe: Online/Internet culture (which I'm surprised it wasn't a booze-related thingy; although maybe exchanging of ideas might still be a common thread here....it just moved from pubs/bars/taverns/coffee houses to internet forums and IRC)
America: Gangsters, murderers and robbers
Japan: Mecha (not just Gundam)
Africa: Safari parks
Korea: online gaming