I think nationality has nothing to do with it. However, any sensory trigger can be met by things that correspond with certain people.
Men who visually resemble any of the men who've abused me put my hackles up. Men who share the same names are harder for me to interact with, and I avoid saying their names. Men who laugh like them make my skin crawl when they laugh. I wouldn't call any of those triggers, definitely slight stressors though.
I think it would be a racist decision if anyone of a certain aesthetic or nationality triggered an attack. If, say, a group of 6 white men attacked you, would you trigger seeing large groups of white men? A single white man? Or would you trigger only if they somehow resembled the attack; clothing, voices, certain words being said, certain behaviors or body posture.
If being traumatized by someone of a certain ethnicity or skin color routinely lead to fear of that nationality, white men would be the most feared demographic in the world. But they aren't. So therefore I conclude that it's just conscious, self-justified, fear-based racism.
I was assaulted by a latino man as a kid. I thought I 'hated' latino men as a teenager. It was fear-based racism that I NO LONGER CARRY because I see how horrible and toxic that is. Yet I've been abused by many white men- I do not fear white skin.
I've also heard the exact opposite argument to defend not-being-racist. "Well I was attacked by a black man, and I don't hate black people, so I'm not racist". THAT is racist BS.