Early game kubelwagon allows you to cap your side of map or half of map on most maps, because it can defeat echelons in 1v1 fight.
Early game you have more fighting squads because you begin with sturmpios and USF begins with echelons so you can be more agressive.
Mid game volks will outfight riflemens thanks to stg upgrade that gives them edge (except lmg rifles that will get nerfed next patch).
Luchs is better than stuart as long as you support him because he is wiping maching or you can go battlegruppe and secure more ground by forward HQ.
Lategame you get free territory lockdown, obers that beat rifles p4 that is best medium tank (except OP cromwell) and you can also call in formidable jp4 or kindtiger.
Commaders are also great, for example specal ops give you panther with mark target - defeats any medium in 3 shots with mark, scavenge gives you JLI - infantry that snipe models below 70% of health and oswind so you can sit on mechanized - puma + luchs into oswind. Both give you infiltration grenades - for 15 munnition they nuke houses and force riflemens to reposition.
Lategame USA is almost doomed if you get kingtiger and jp4/2 rakettens
Kübelwagen can´t beat RE. Not even a close fight.
Volksgrenadiere never outfight Riflemen. They might win with STG against unequipped Riflemen but who plays with unequipped Riflemen mid-game? I don´t know why people really overrate Volksgrenadiere so much. Even Vet 5 Volksgrenadiere lose to Vet 3 Riflemen since Riflemen get better vet bonusses. Un-equipped VOlks and Riflemen fight -> Riflemen win. Equipped Volks and Riflemen fight-> Riflemen win. Only at max range Volks have a 50/50 chance. Any other range and Riflemen dominate them.
I can show you that with cheat mode if you don´t believe it.
Jäger Infantry does OK but is super expensive to re-inforce (37mp).
You may have 1 more squad (if you don´t get Kübelwagen) but that´s worth very little since USF doesn´t need to fight one Volksgrenadier squad with two Riflemen squads.
Obersoldaten suck in most close games because of two reasons: 1. They need to fight vetted Riflemen. 2. They are super expensive and prone to get wiped by in-direct fire, basically glass cannons.
Nothing you said is a clear advantage for OKW other than being able to cap quicker early game.
My opinion still stands USF>OKW. Maybe that is also the reason I see OKW so rarely in competitive games.