So my counter question to that is where is USFs weakness? Or soviets?
My personal take on the factions is that USF is the "strongest" faction in that it has the most powerful things. SOV is the actual "strongest" or the most effective because of its versatility and how it can field effective counters to everything, often without a fuel cost.
As a result, I believe that USF will try to "out-stat" you in a sense in which it will try to do whatever youre doing, except with something more powerful. The key here is to not play that game and exploit the faction's lack of tools. USF struggles with garrison clearing and cover denial (thats probably repeated a lot on this site, isnt it?), so spamming cover usually works to your favor. Incendiary nades or snipers and mortars can help you take back the cover position if you lose it while USF doesn't have anything as convenient. It's easier for you to lock USF in place than it is for USF to lock you in place, so if you ever force a lot of his units to retreat and make a forward defensive line or gradually move the line up with smaller victories, you can hope to get USF in a strangle hold.
Furthermore, USF's team weapons are, as a whole, lacking. MG42s and ost mortars combined are pretty effective against usf since the combination is stronger than a .50 and a USF mortar. Also, the non linear teching means that its possible to exploit the lack of AT guns if you get a medium tank out early enough, or win in the combined arms game if he didn't tech lieutenant.
Soviets are different in that everything can usually do everything. Nearly every soviet infantry squad has AT (AT which usually snares, at that). A lot of their AT options have anti infantry barrages. This means its harder to exploit any fundamental weakness. Durable weapon teams and snares everywhere usually mean pushing is difficult. However, well executed pushes can still break the line and can be more devastating than usual. Flanking a weapon team then deathlooping it is a good way of making a soviet weapon team into an axis weapon team. If you're not confident in executing pushes, then spamming indirect fire and smoke is the next best option. Soviets are great at turning the match into a stalemate now, so you have to be patient; whether thats biding your time for an opening, or waiting for your indirect fire to do work. The point is, you can't go into a soviet matchup hoping for a bunch of infantry squad vs infantry squad engagements or hoping to make a bunch of vehicle pushes.