The Vailian Republics are just another (former) colony like Dyrwood. Even Old Vailia (which is located far to the south) didn't exist during the Engwithan Empire and is located several thousand miles southwest of the Eastern Reach, probably on the same "old world continent" like Aedyr.
As far as i can tell (referring to Kana), they had contact to cultures in the Rauatai Gulf which they influenced. And it's safe to assume they also had contact to other "neighbouring" cultures (on the same continent), e.g. the Ixamitl plains.