France was a nation in medieval times. I think you mean to say that the modern concept of nation-states wasn't a concept, back then. Which is true. However cultural identities did exist. And thats what people refer to when you talk about ''The English'' or ''The French'' in these times. The Germanic people have considered each other the same cultural group since they met the Roman legions (not completely true, but you get the idea).

Its why in the Dutch national anthem, from the 16th century, we still sing that we are of ''Dietsen'' blood. Which means that we come from German blood. The English name ''Dutch'' originates from that same sentiment.