Ooo I really like this. What if it's Bucky who isn't all that traumatized by it? Sure, it was awful and he absolutely hated it, but he's so used to being raped by hydra that he's just learned how to push his feelings of disgust and revulsion out of the picture so that he can keep going. He's just Not Dealing With It. And maybe he will experience some PTSD later on when he actually does start to deal with it, or maybe he won't.

Meanwhile, Steve is suffering these horrible nightmares and he flinches away whenever someone touches him without warning, and he's really confused about why Bucky isn't reacting the way he is. He starts to think that maybe he's overreacting and it really wasn't as bad as he thinks it is, or that he's weak for feeling this way. And you know how stoic Steve is. That'd make him work extra hard to suppress everything and act like he's fine.

I wonder if Steve knows about Bucky's past rapes though? Maybe Bucky's hidden this from him and the other avengers so that he can keep on Not Dealing With It. Or maybe he told Steve about it all nonchalant like, in an attempt to make it seem like he isn't that fucked up by it. Or maybe Steve and everyone else found out by accident when like a video clip or something of him being raped was released on the internet. But whatever the case, Bucky's blasé attitude about it just makes him doubt himself even more and he shuts in on himself and just suffers the anxiety in silence until he bursts