I have a generic American accent. People can tell I'm American, but they have no idea what region I'm from. I'm guessing I must have picked it up from watching TV, or something. My father has a Boston accent, and my mother has some sort of British accent, yet I don't sound anything like either of them.
I don't know if it would be considered a speech impediment, but I tend to mumble, use lots of "uhhhs" and "ummms", and I have trouble expressing any kind of emotion in my voice. It's not automatic for me like it is for most other people. I sometimes have to fake it, and then I end up sounding insincere because I can't do it convincingly.