Live in Ohio, and all of the bedrooms are upstairs. I haven't seen a house that has the bedrooms split up that isn't a really old home (where, most likely, the master bedroom was something different back in the day or something)
I remember when I was younger, my family had a split level home where there was the front door, then the living room, kitchen, garage, etc. and you could go upstairs to the bedrooms, or downstairs to a finished basement/another family room thing. My mom and dad turned that area into the master bedroom so that we could each have our own rooms upstairs, but that wasn't initially how the house was set up, just how they maximized space.
If it came down to it though, I wouldn't feel comfortable having my bedroom an entire floor away from my small child(ren). I just think of how DS, if he wakes up in the middle of the night for whatever reason, will come get me in my room. I wouldn't want him to walk downstairs to look for me.