USN  shouldn't be using torps.  If you must the Somers has 3 launchers and a versatile launcing arc.

i would say the brooklyn

The best ships to use usn torps on are all FFs. ;)

The most effective ship to use would be something as small as possible, that can hold enough torps to enough damage to actually sink something.

So V2CxBongRipz's suggestion would be best, or one of the DDs.    ...maybe.

If you have high lvl, not crappy Engis.. the pensa would work,  because with short range US torps you will have to get close and you would need the speed cap to be able to dodge all the BB's firing at you.  

Torpwhore moltke. Defintely what you want. You have the same attack ability as a Kita, if you use the T2 x5 launchers. But Kitas don't have proxy torps... heh heh heh

But to be more relevant, I would pick one of the following - the Pensacola, Northampton, Portland, New Orleans, or Brooklyn for torping. They all have 4 T battery slots that in all but the Portland's case are too tiny to carry much else that's useful. I don't remember nowadays just how good a torplauncher you can put on them, though.
The Cleveland, Baltimore, Alaska, and Guam all have bigger T slots, and can still maneuver, so you could still launch 4 torps to a side. However 2 of the 4 are shared, that is, if you shoot either of those 2 mounts to the port side, you cannot shoot them to the starboard side until they reload. These have only 6 launchers, so to speak, but you may be able to mount better torp launchers on them.