“had a much more advanced submersible than the “Hunley” in the “Intelligent Whale”
That might count if the Intelligent Whale had been launched during the war, but wasn’t finished before the war had ended. It was laid down in 1863 but not completed until 1866.
By contrast the Hunley not only was finished, it sank the USS Housatonic.
And sank itself. Hardly a glowing record.