The part ordering is supposed to be (used to be on German site) on the page of the set, but when you go to a set where you know parts are available there is no link. The link does exist on the German site page so I think it has to do with the site version since it was never there before for the US.
However, yesterday on the Building Instructions page linked from the lowest left of each page there was a radio button that lets you switch to ordering by parts number. It's gone now, which makes me think they messed up and weren't really supposed to have that there for the US site.
I just sent in an emailed parts order to the US team, so I expect we will hear early next week if there are changes in process in the works for them.