There is a book written by Michael Gammon entitled “Operation Drumbeat” which details Germany’s U-Boat attacks on the East Coast shipping at the start of WW II. The US Navy was totally unprepared for the U-Boat attacks.
A great read!
If the Germans utilized the U-Boat more strategically,the war very well may have turned out quite different. That goes for their under utilization of their air power.
So was the German navy. Germans never had enough u-boats. The battleship Bismark weighted 41,000 long tons. A type VIIC U-boat weighted 759 long tons. 54 U-boats could have been built instead of the Bismarck.
Adm. King refused to listen to the British advice to run convoys instead of one ship at a time. His argument was lack of escort vessels, but he hated the British and wouldn't listen to them. Lotta people died because of that.