In case you do a SL:
With a BB alive paired with your CR you will need two additional Ftr’s and have a 90% chance to win and deflect a scramble. If you add a DD you make it to 98% chance of winning the sea battle.
With a BB alive + CR + CV you will need to add one Ftr to make arround a 94% chance of winning the sea battle. Add another Ftr to come close to a 100% chance.
Without a BB you will have to add more Planes and/or newly bought units/ships to make a Allied scramble less likely.
The CR + 3x Ftr’s + a CV to have a 94% chance.
However, a surviving BB is allways helpful and is a high valuable piece.
But it depends on how you will use it.
If you are able to keep it, combined with a few ships and planes who are watching over it, making a Allied early tactical landing on ATL side less possible and the US player has to spend more IPCs for the ATLantic.
Less stress for Axis Germany.
If the BB is gone and not at hand, you will have to buy units to protect the coastline and purchase a DD blocker every now and then to prevent quickly build US strongolds on European side.