A temporary 2D-mode-only restriction is placed on some circuits. They should be lifted within 48 hours, and the delay is just the time stores take to review app updates. The 3D versions of the affected tracks have already been fixed, but app review means we can't release them today. They'll be with you soon!
The tracks which will temporarily be restricted to 2D are: Monaco, Britain, Germany, Japan, Mexico, Russia, Canada, Turkey and USA. The rest are all 3D now and they will all be back in 3D in a couple of days.
EDIT: Malaysia has been added to the list of circuits.