I'm concerned about game ballance on the American side of things.

[danoh]

If the torpedoes are true to life, then we can also use knowledge we have to compensate for the bad torpedoes.

American torpedoes at the start of the war had two problems: they ran deeper than set and the exploder was faulty when using impact rather than magnetic detonation. Samuel Elliot Morrison summarizes these faults on p. 495 of "The Two Ocean War."

"The first defect caused the torpedo to run ten feet deeper than set, usually so far und a ship's hull that the magnetic feature was not activated."

and "[the second defect, the impact firing pin] proved too fragile to stand up under a good, square, 90-degree hit; normally it would set off the charge only if the warhead hit a ship at an acute angle."

and finally, on page 496: "It was not until September 1943 that United States Submarines had dependable torpedoes."

If all this is accurately recreated in the game, then you should be able to compensate for problem 1 by shooting your magnetic torps on the surface, which would make them run 10 feet deeper, but still shallow enough to be triggered by the ship's magnetic field. The second problem can be overcome by shooting at acute angles.