Indeed not. Immigration control and passports did not arise until the first world war, in fact. Border crossings were quite open until then. But culture was

Indeed not. Immigration control and passports did not arise until the first world war, in fact. Border crossings were quite open until then. But culture was not insignificant. They did not define borders (and some might argue they still don't do to this day) in any way, but they guide monarchs whereto increase their realm's size. But in a way, while culture didn't define borders, borders did define cultures. Where they speak French or German is largely attributable to the duchies and kingdoms where they spoke French and German. The arbitrary borders of Europe can largely be attributed to this.