This sentence doesn't make any sense. USF has a fraction of the munition sinks Ostheer and OKW do and you yourself said we see few demo's from them.
What? No. USF has weapon upgrades like Ostheer and OKW but up to
two, static MG upgrade like Ostheer, pintle guns like Ostheer on their medium (though less overall on their tanks) which cost 10 more, and some units that are walking munition bleeds to function in addition to a bunch of smoke abilities (none of which are free).
REs: If you're using them in combat regularly, you're using suppressive volley 'cause it's not like it does damage.
M20: Armour skirts and if it lives long enough, it exists for placing AT mines because it dies in two AT hits while requiring close-range to do damage and losing it costs you these mines.
57mm: If it's at least a PIV, the 57mm needs to chug AP shells.
Stuart: Basically the only thing really good about it is has a bunch of abilities (which are a bit poor themselves but that's another story).
Major: If you're using him as something other than a retreat point, you're using his (mostly horrifically overpriced) call-in abilities.
Additionally, Rifles' vet basically requires munition spending to be useful, as they get less accuracy from vet 3 than other combat infantry while gaining a large decrease of their abilities' cooldowns.