The features on the world map are not to scale and their relative locations are symbolic at best. Truce, Guardia Castle, the Millennial Fair and the Cathedral should all be within a days journey instead of spread across half the continent. However, the landmasses on the world map appear to encompass the entire globe, which can be circumnavigated or viewed from space. Assuming the planet must be similar in size and composition to the earth, its equatorial diameter is 40,075 km. Based on this scale, Truce, Porre, Choras and Medina are separated by thousands of kilometers.
I agree with Guardian_of_Ages' comment about the logistics of governing a large territory. Zenan is a vast continent. Most likely, in 600 AD, the Kingdom of Guardia only covered a small portion of the northern continent and many other unnamed countries existed. The time period seems similar to Europe during the Crusades as far as technology and politics.
Slightly off-topic...
Civilization in 1000 AD is comparable technology to 1850-1900 (refrigeration, typewriters, steam power), however there was no industrial revolution. The population is at pre-1750 levels (< 500 million), most people live in rural areas and the primary industry is agriculture. However, scientific knowledge is closer to the present because Lucca and the Guardia military were capable of developing the Dragon Tank, Gato and the Telepod. I would attribute the lack of widespread industrial progress to a lack of fossil fuels. (I guess Lavos ate them.)