When should Germany have surrendered?

[Grumbler]

"By 1941 the war in the Atlantic had been won."

Completely wrong! The Battle of the Atlantic was won in March of '43.
What would you accept as evidence? There are reams available, no point in producing a 15,000 word thesis on the subject, which I believe has been done several times. I'm getting started on a house renovation project and don't have access to my library, so in a couple of weeks, I'll be able to give you chapter and verse on this subject. Working from memory, the battle of the Atlantic didn't peak until late '42. In '41 is was just getting started.
And I stand by my statement that without American aid, England was doomed.
It was American Jeep carriers, operating with B-24's and PBY's from the various Island bases acquired in the Destroyer deal that beat the U-Boats.
And the 300,000 rescued at Dunkirk WAS critical to England surviving until American might could be brought against the Germans.
Did you know that when the Ban was called, men were showing up with Longbows? While I would never laugh a Longbow, it wouldn't be my weapon of choice against Mg-34's. If the Germans had used the paras they dropped on Crete to grab a airhead, or a port along the English coast, It would have been over for England. The Germans ran out of bold at just the right time to save England, since England was incapable of saving it's self in the Summer and fall of '40.