Why do American subs have a less test depth in comparison to a German UBoat?

[A Soviet Fanboi]

So I was doing my usual patrols in SH4 FOTRS, then I suddenly got attacked by a G4M1 Betty Bomber(I forgot to turn on my SD radar). I recieved a hull damage of 83 and I crash dived immediately after shooting down the bomber. I was in a depth of 113ft and suddenly my Chief Engineer spammed with words like Compressor Damaged! Pumps Damaged! We have heavy floading! Etc,etc. I was surprised and checked on my damage and yes it was really serious but it was too late and I got crushed due to water pressure. But the thing is I was at a depth of 113ft only and still I got crushed, 113ft is like 35ft and that's quiet less. I am damn sure that if I was on a type IXC u-boat on SH3 (Because I haven't played the u-boat campaign in SH4 yet) I would have survived. So the question is, why did American subs had a very weak hull or a very less test depth in comparison to a uboat?