If in 1939 America and Germany had swapped their torpedoes, it would be hard to know who would have benefited. There would naturally have been major difference. For example, German contact pistols did not fire on oblique hits while American pistols broke if they struck normal to the ships hull. Both magnetic fuses failed and neither ran at the correct depths.
What would have happened if German torpedoes had been properly tested?
What would have happened if German torpedoes had been properly tested?