Interactive map of every bomb dropped on london from oct 1940 to June 1941
I bet that was a big treat after months of sea. From stories and photos I've seen, German subs were "no damn fun" when they left port for a long patrol. There was food and other supplies stuck everywhere, on the floor in crew's racks, ridiculous. I don't know that US boats were quite that bad.
Both the Germans and the Japs got uncomfortably close to our shorelines. "We" the big, the all knowing, Americans, refused to listen to the Brits, who at the time we entered the war Dec 7, had already been supplying "stuff" to the Brits via the Merchant Marines , certainly unsung heros and victims of that war. We refused to take the Brits advice concerning sub hunting and convoys for a very long time, and east coast places line Coney Island refused to shut down over losing money. The Germans happily used coastal lights for navigation and to silouette targets!!!
One thing that was the downfall of the German "wolf packs" is that the commanders "back home" insisted the German subs stay in touch via radio, so we just DF'd 'em, a fairly easy job back then, and both SONAR and RADAR had made some inroads by then.
An aside, you have to understand that the cavity magnetron, claimed by the Brits, has really not changed very much since WWI, in every microwave oven you see It essentially is a "one component transmitter" needing nothing more than appropriate power (filament and hi volt.) to make it produce RF output.