URMMM... Guys... How come I cant change the Phone Language? Its currently set to US and adding other languages doesn't change the fact! I'm using the unlocked AT&T version of the M8.
Go to Settings -> "Time+Language" -> "Language."
Once you're there tap and hold the language you wish to be the display language of your phone. Move it to the top, restart your phone, and you should be all good to go.