The copy of U-571 that I own (don't worry it's a cheap thai knock off) has an extra which one of the men who retrieved the enigma machine and code books from the U-110 tells the story behind the capture.
I also read the US need to capture their own engima machine as the British wouldn't give them the details, despite the US giving them the details of the Japanese codes. Winston Churchill didn't think they would be able to keep it secure. He was right in doing so. The Germans had cracked the american radio codes and had used the information to help Rommel in North Africa.
This is why the US went after the U-505. This is also listed in the credits of the movie, along with the three previous British captures.
For the record, I think the moive is light weight fluff and doesn't do justice to anyone on either side. Das Boot on the otherhand, is far more engaging
