Col7777,
Great work and great news! This proves that a package like 'Pacific Aces' or similar is possible for SH3 as well!
BTW, I remember one of the first 'World' mods had an American playable sub included. Think it was a Gato. It had the interior and general performance of an IX sub though, so it had it's limitations. I never tried it, so I don't know if it was recognised as an enemy of Germany.