I take a slightly different view to the early resistance to convoy-strategy early in the war...
1. The USN, like everybody else, was short on destroyers needed to guard the merchantmen.
2. Those we *DID HAVE* were already convoying Lend-Lease over to the UK (or as far as the mid-ocean gap if you prefer).
3. It seemed unreasonable to conclude that German Type VII’s had the range to reach the US East Coast. The Germans created re-fueling, re-arming submarines, the so-called “milch-cows” that were analogous to USAF air tankers. I doubt the USN was aware of them or realized the implications.
4. Adm. King takes the hit for this. He hated the Brits and the feeling was mutual. So when the mistake got made he was the logical guy to pin it on by virtue of the politics of it as much as his position as CNO.
It wasn't the Type VII's that were tearing up the eastern seaboard (at least, not initially); it was the Type-IXs. (And if the USN was in the dark about their existence, add this one to the pile of evidence of how caught off guard this country was as the threat of war grew.)
Read Operation Drumbeat (Michael Gannon) about the U-Boats that sank ships up and down the East Coast in 1942, taking the lives of some 5,000 men in the process; that loss of life as well as the freedom with which these U-Boats were able to operate unmolested is still one of the best-kept secrets of the war.