Im struggel on with my USF but without any succes!...snip
When everyone says "USF constantly assaults" it doesn't mean throwing bodies into the meat grinder. Typically it means you have to be aggressive and try to seal out the game before late game hits where USF is the weakest. To do that, you have to be able to take points, cut off Fuel, and control VP's, and of course win engagements.
USF has to switch between splitting up troops to enable wide flanks and attacking a singular point with everything you got. To enable wide flanks you have to have riflemen go a long way and have another riflemen squad scout an enemy's turtle position. Engagements will last a while if you are in a good piece of cover or are too far to take damage, which is how your other riflemen squads flank. USF's effective range is mid to close, but if you are in a great piece of heavy cover it's often better to stay there in a firefight.
Now, if they are super entrenched it's sometimes better to go around and cut them off from their points to force them out(I've had people sit 2 mg's in a building nearby as I decapped his stuff). However, let's say that wide flanks aren't feasible and you are forced to assault a turtle position. Your options in which case would be to smoke and assault with everything you got(Smoke MG's, squads in cover) or build a pak howie and grind them out. Don't pick engagements you'll never win, you'll just bleed. You need to pick engagements you can break through with.
Late game if you don't have premium commanders you are pretty much just spam Jacksons, Priests, or M10's.
OVERALL: Looney has listed some build orders, but if you are new as USF and a new CoH2 player I just suggest going 4x Riflemen into captain into either Stuart, Ambulance, Nades, Pak Howie or Weapon racks to fit the situation. The LT tier requires finesse and if you can't pull it off you may get shut out.
ALSO PRO TIP: If you want to know if a building is occupied, tell your troops to occupy the building from far away. If the building glows red it means a unit(mg probably) is in it. You then cancel your dudes order and left click the building. If it's an MG it will tell you what direction the MG is facing. It's a bug I think, but it'll be your best friend. This will give you the information you need to better plan your assault.