Besides the fact he's making a bunch of assumptions and nobody actually knows, I'd say the futuristic 1950s American backdrop likely doesn't allow women in the US Army to wear power armor. That would just be my guess though! Gender roles and all.

Heh, quite possibly . Still, Bethesda themselves do seem to steer clear of portraying stereotypical gender roles (or at least, of emphasising them), certainly in Elder Scrolls and as far as I can recall in FO3.

And they may take the attitude that the player character (whichever gender is picked) is just one of https://en.wikipedia.org/wiki/Mariya_Oktyabrskaya who doesn't conform to society's familiar roles. Of course, Mariya Oktyabrskaya wasn't the only one, and those were times of great pressure on a society that was very definitely not like 1950's USA. Still, it gives Bethesda plenty of wiggle-room, and it would make writing dialogue and opening quest just a little easier

I always figured at some point the Prewar fallout America went through their own social reformation and all citizens gained equal rights and acceptance into the military. Would explain why racism amongst different human "races" doesn't seem to exist.

Well racism is always a divisive issue, even today, and not something many video games want to tackle for fear of alienating an audience (in the US anyways). The same could apply to gender roles, but again it's all speculation. Regardless of whatever roles males and females had in pre-war ficticious USA, everybody is without a doubt equal in the wasteland (unless you are a super mutant or a ghoul).

I'm just looking forward to using power armor for the first time and tearing that death claw apart.