the yanks have already developed a flying torpedo, air to sea or sea to air. A slow moving target like a non-nuclear sub would be an easy target. I was reading a book on cold war submarine technology, in the 1950s the yanks covered the north sea and parts of the Atlantic in acoustic listening devices to track Russian submarines leaving the Baltic sea. Submarine warfare is very expensive as its measure versus counter measure with only the US, Russia and the yanks able to justify the spend.
These Adelaide built submarines aren't really effective counter measure against anything.
If you want to read a good book on fighting a submarine war, Iron Coffins by Herbert Werner will have you on the edge of your seat. Another one worth reading is The Japanese Submarine Force and WW2 by Carl Boyd, it details how badly the Japanese managed their submarine force.