Fair enough, I've been playing long enough to where I should be top 10, but I'm not. However, when I play axis and other allied factions, I don't have these problems. I spent about a month not long ago playing soviets and didn't have a problem. The units were effective. Sniper is kind of slow to pull the trigger, but still got the job done. Still can't really do lol panther stuff, but tank battles were fine.
If you've tried Soviets (which are good in their own way, to be fair), you'll find that Riflemen are really obscenely good compared to pre-7 man Conscripts. Riflemen are the best mainline in the game and stomp grens and volks in a vacuum.
My biggest complaint with USF is that the roster isn't complete - no non-doc flamers, need to go m20 or use a doctrine just to lay "real" mines, no rocket artillery, no sniper counter. If your complaint had been that USF has restrictive teching and lacks many tactical options due to not having certain units, I'd have wholeheartedly agreed with you.
Tldr: USF units are very powerful, but the faction as a whole has plenty of weaknesses, some of which are irritating (retreating units getting stuck in the bloody pizza base) and some of which are way too painful, like not having flamers on a garrison-heavy map or having to rely on pack howie RNG to counter snipers.
By the way, in your initial post, you mentioned you kept REs at mid range. When flanking an MG you should run up to knife-range always. Especially with REs, who're practically only able to do damage when bayoneting people.