USF is the strongest faction in all gamemodes, even in 4s.
If you don't know how to progress watch people people USF in Live Games.
In 1s vs Ost > 3 rifles > LT > m20 > ambu > Cap > calliope / Pershing / Major >
In 1s vs OKW > 4 rifles > Cap > Stuart (with captwin ability) > ambu > pak howie > calliope / Pershing / Major >
after first vehicle and ambu get nades/bars depending how you're losing engagements.
Gren/volk spam > bars
Support wep spam > nades
GL HF
4 units holding together an entire faction, the fact that this is the top method of using the usf is damning evidence that the overall design is a bit off (they're not weak just one dimensional)