The oldest boats in the the U.S. inventory (S-class) were pretty slow, only about 14.5 knots surfaced and 9 knots submerged. As the war and submarine designs advanced, surface speeds improved from 15 knots to 21 knots, with an averaage of around 19 knots for most. Submerged speeds remained steady at around 9 knots.
During WWII, US subs were named after fish.
52 subs were sunk (lost).
52 US subs were lost in WWII.
Carriers, Battleships, Cruisers, Destroyers, and Subs
German subs sinking the Lusitania and the Zimmermann Telegram.
Counting warships & merchantman, US subs sunk about 1,000 vessels.
German subs fought "Guerre de Course." (Merchant Sinkings) Japanese subs fought "Guerre de Escadre." (Warships vs Warships) US subs fought both.
No WW II was fought mostly in the European, North African and Pacific theatres of war. Although German subs occasionally sunk shipping off the US Atlantic shores and less often the subs were sunk there by US forces
US Subs patrolled the world's oceans, including the Vietnam coastline. Other than possibly any covert operations, US submarines just patrolled, and kept an eye on any Soviet subs working in the South China Sea (Vietnamese Coastline).
We entered World War 1 because of a German submarine attack on U.S. merchant ships in 1917.
It was partly the sinking of the Luisitania and the fact that the Germans declared that they would use their subs against any ship they wanted to.
They were there to sink as many ships as possible. Some were given the role of landing spies but that was always subordinate to the role of sinking ships.