Suppose the Benelux countries had a fourth neighbor- a buffer state beyond the Channel, between the British and the French, based around Calais. Could such a country exist? What culture would it have?
You mean a British Calias that becomes (and remains) independent at a later stage? Could be possible in a Europe with a weakened France, I guess. And you need a weakened France for Calais to remain outside France.
As for the culture, probably some combination of English and French, or even possibly English, French and Dutch/Flemish. Calais spoke a Dutch/Flemish dialect in the past and I am uncertain when it switched to French. If Calais was still Flemish, I could see the English promoting the Non-French culture to make Calais more distinct from the rest of France (but this would only work if there was still a significant Flemish culture left in Calais and I am uncertain if it still was)
Kinda less interesting if it’s just part of a Greater Belgium. Though I suppose having to deal with Flemish, Walloons, and Picardmen would be funny.
How does Burgundy fit in with this? Could there be a rump Burgundy that included Calais but not Benelux?