I'm playing the Grand Campaign as France on H/H.
I control the Western Mediterranean included the trade nodes along the North African coastline and was making good money through my trading port at Genoa. I also had trading ports on the Atlantic coastline, but the British navy was blockading them. (For some reason the British AI has made no attempt to enter the Mediterranean with its powerful navy. That's nice on one hand, but disappointing on another.)
During the game, I decided to build a trading port in France on the Atlantic coast. A single British frigate blockaded it and there went all my overseas trade! Everything! My sea trading routes with the Italian states and all the income from my 5 controlled trade nodes. Genoa is still open for business, but for some reason a single frigate blockading the capital province's port shut down all my overseas trade.
So I just want to get this right: if you build a port in your home province then all your overseas trade will go there? And if that port is blockaded then your trade will not be redirected toward another open port, but will instead be completely blocked? So unless I want to fight costly sea battles with the Royal Navy in the Atlantic then my best option is simply to destroy the port I built in France with the assumption that Genoa will once again become my main port. Is it me or is this a rather silly way to depict trade? In RTW and M2TW, if you blockaded a port then you stopped the trade for that port only, not the entire opposing empire! So why isn't it that way with ETW and now NTW?