What shipping?
The board has been reset, this is not a replay of OTL WWI/WWII. Shipping lanes will be different.
Besides Halifax/St.John (which I do not see the UK losing, unless very unlucky) military supply convoys, there will be no Entente flagged Europe-North America traffic.
Ships sailing from the Carribean/Colombia/Venezuela will take a slight detour towards the east, closer to African and European shores, i.e. Trinidad - Cabo Verde - Canaries - Madeira - Portugal - Biscaya. Some shipping which normally would had sailed to Nantes or Bordeaux might go to Marseilles instead, to get it out of harm's way.
Good luck with raiding the waters off Madeira or the Western Approaches from Boston using German battlecruisers.
E.g. - Boston to Lisbon is c.2,8Knm/c.5K km.
SMS Seydlitz - 4,2K nm at 14kn. Not much wiggle room, and recoaling on the high seas was
not a thing.