How one nuclear attack submarine would affect different wartime navies

What difference could one fast nuclear attack submarine make for a Second World War navy?

It would be tactically dominant but strategically limited as a single hull, with its mission varying from commerce attack to hunting U-boats, raiders, or carriers.

For Germany, an SSN's underwater speed and ability to attack without surfacing would make contemporary escorts extremely hard pressed, although a single boat could not dominate the whole Atlantic. The United States would gain a faster version of the commerce-destruction campaign its submarines already conducted against Japan. Britain would likely use the boat to intercept U-boats and surface raiders before they reached open water, while Italy might exploit its speed in the Mediterranean. Japan is pictured holding it near major sea lanes in hopes of ambushing an American carrier, showing that the same technology would be shaped by each navy's priorities.