@Sirkem_Iskof well first Euralia as stated is a Kingdom. Though it is fairly large around the size of maybe china.
Its large size is due to the fact that it was once an empire that expanded ruthlessly in a period called the era of ruthless ambition.
At the present the borders are ambiguious with several western provinces looking to break away.
As for Yhunia it is relatively smaller, maybe 1/4 the size. Though they are a collection of several nations ruled under an entity called the council of lords.
The border between these two are important as there are three main rivers that served as an important route for trading with the northern countries on the continent. And by extension, also trade to the nations beyond to Triferian Ocean to an as of yet unnamed northern continent.