I feel your pain, man. This is literally me every game against OKW as US Forces. I got into 1v1 recently, and I have won all my games against Ostheer, no matter the rank or strategy of the enemy player. Sadly, as soon as I load into a game against an OKW, I lose, it takes me a long time to lose, but I always lose in the end. They claim that OKW takes a long time to collect resources, but they have such effective units to take the whole map away from your rifleman army early game. I have tried using M1919s with my Rifles, but the OKW infantry still dominates me (Especially those grenades the OKW infantry have that can wipe a rifleman squad if you aren't careful.) I usually build 4 rifles, skip ambulance, get a Lt., then a Cpt., and lastly a Stuart. By this point I am replacing my lost riflemen and giving them Bazookas or M1919s. It seems like Maj. is out of reach at that point. I lose my Stuart to a puma or a shrek blob. I have tried various tactics, but it always comes down to the same result. I can keep a game going for a long time with my geared up riflemen, but it's merely a waste of time.
Any strategy I could use to be on top of OKW?
You need to work on your build order mate watch some replays of pros.
Try this build for early map control vs OKW, choose Rifle company, get 2 RF + 1vet callin RF(handy against those Kubel) and get to fuel point and guard it, build FP with REs if you have to. get LT out and now based on your map control decide on calling M20 or holding back for M15 by doing this you are forcing him to get puma out. if you give him even 1 fuel point you will see a puma in under 6-7 mins so get your zooks researched asap.
i prefer M20 against OKW as the mines will kill puma in one hit plus you get early map control and for M15s cost you can research both BAR and zooks and keep calling in vet RFs.
watch out for AAHTs they are pain to deal with if you go this route. after this get to major if you have upper hand. if you dont you have lost the match as the next thing you will see is a luchs and its hard to deal with in this build order.