The bathroom isn't in a separate closet--there's just a small room for the toilet inside the master bath.
We moved out of state about a year ago, and we were surprised to see that a lot of the master baths here have the toilet right in the open part of the bathroom. It's very odd when you're not used to seeing it that way. The house we got has the toilet almost in its own water closet, but there's no door. The doorway is open, and it's a bit too small to actually install a door there (we asked our contractor). You can't see in when you enter the bathroom, though, so we're okay with it.
That's it. A separate room, usually at one end of the bathroom. Ours is small, only about 3 feet wide by 6 feet long. With 10 foot ceilings, it's not claustrophobic to have a toilet in a 3 x 6 room. Aside from a cabinet above the toilet, the only thing in there is the toilet. That means the bathroom itself can be used for all the other bathroom stuff if someone has to have a wee while you're showering, taking a bath, applying makeup or getting dressed. If the toilet is out in the bathroom, the entire bathroom IS the toilet.
Unless it is a very inexpensive house or older than 25-30 years, you will rarely see a toilet as part of the master bathroom here. It will have its own little room connected to the bathroom. That's TX. I don't know about other states.