There are a lot of fine distinctions here that I was afraid to bring up or sort through.
Accountable implies somebody else is holding me accountable. This would occur if I had managerial authority for example.
Taking responsibility implies that I’m not fobbing off moral ownership on somebody else. If somebody forces me at gunpoint to litter, I might not take responsibility for littering. But say I’m in a crowd surrounding 2 angry men and I start chanting “Fight! Fight! Fight!” I wouldn’t say I am responsible for the forthcoming fisticuffs. I am however responsible for my own behavior, which objectively increased the probability of fisticuffs, which can have real consequences.
So taking responsibility means I am not redirecting blame.
Utilitarians such as myself take a broader than average view of responsibility. In fact, that’s a valid criticism of that particular moral system.
PS: Appropos nothing, the law has the concept of joint and several responsibility. So if 2 people sign a $1000 lease, person A is responsible that the entire sum gets paid, as is person B, as far as the landlord is concerned. The point being that responsibility for an incident doesn’t have to sum to one.