Other countries in Fallout ( the game )?

Ok so in the game Fallout you are in America right? But what is it like in other countries like Japan, England, Russia and so on and countries like Africa,Antarctica, Greenland and Iceland shouldn't have been hit by the nukes and most of the radiation from those countries would be gone by know? I was just wondering why they don't travel to them countries It popped into my head when I was playing Fallout New Vegas this morning ( that game has nothing on Fallout 3 except the companionship wheel )