Actually, the USA had 32 submarines in service in January 1914. The problem is deciding how many of these were actually combat-worthy (and so should be depicted in the game), and how many were just experimental, training models, or basically useless.
Certainly the six A-class and three B-class shouldn't have counters IMO - they didn't even have crew accommodation on board, and were purely used for harbour defence. If anyone is really troubled by their absence from TGW, I'd suggest giving Manila (which is where they were stationed) a point of coastal fortifications.
Likewise for the five C-class, which were based at Panama.
That leaves 18 submarines from the D, E, F, G, H and K classes (imaginative names
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
) - counting these as one flotilla instead of two is possibly a little harsh. However, compared to German submarines the American ones were tiny - half the size - and carried only 66% of the number of torpedoes a German U-boat had available. So I don't feel guilty about short-changing them.
I can only imagine Victoria counted 5 U-boats to the flotilla instead of 10, and included even the A-type minisubs. (Which, incidentally, had to be taken to the Phillipines as cargo on board transport ships - they could never have reached there under their own steam.)