USF have little reason to have so many stock indirect fire option to begin with, a T0 Mortar, the Pak howitzer, Scott and Major barrage.
SOme of these option should simply be move to doctrines.
Let me just take this words for the sake of my argument. While i agree with this statement (USF has many indirect fire options) and also agree with elchino7 about most of these options overlap their intended roles aswell.
The only design wise objective idea about it would be that USF has an indirect fire tool for each timestamp of a game, super early mortars, midgame powerhouse pakhowies, late game mobile scotts.
The design has some unique aspects and i would like to highlight that, pak howies are solid indirect damage dealers and can outclass but not counter axis mortars. Side note here, since many people mentioned LeiG as an axis analogue of pak howie, i would mainly disagree, but admit that are some common points when comparing 2 LeiG vs 1 pak howie performance. Ideally axis stock indirect fire (OST mortar, OKW LeiG) are early options with some midgame presence, pak howie is a mid game unit with late game presence.
I would rather compare LeiF with pak howies (obviously LeiF as a late game indirect fire unit) even when nothing good can be achieved from the comparison itself.
TL;DR
IMO USF has many options because its design is to have an ideal indirect fire for early/mid/late game
Doctrinal indirect fire tools add even more stages (MTHT, PRIEST)