Ok, in N. Ireland, 40 years ago, Neeson chose to search for a victim based on his skin colour, not religion etc. So, yes, there were the troubles, but also, yes he was acting based on race.
This history of racism you uniquely ascribe to the US played a part. It's a stereotype that crosses borders.
It also wasn't an assault, he wanted to kill someone. That it wouldn't technically be a lynching is because he didn't believe he was punishing the perpetrator, just any black man. Hardly makes it better.
And definitely, as a Hollywood actor, promoting a film, he knows the context when he's told the story. It's telling that he thought he should tell it like this. If he was telling this story out of contrition, surely he'd have done it differently.