In most conversations about circumcision, I've noticed we always say, "I am/am not circumcised." Or we ask, "Are you circumcised?"
We don't say, "My penis is circumcised," or "I had a circumcision."
I think it has to do with identity. Our penis is such a part of us, we don't separate it in any way. What happens to it happens to us.
What do you say, or how do you ask, when the subject comes up?