Same here, US3 is down, app doesn't work either.
(The app also has another annoying problem because of this though, after trying to login on the app, it keeps prompting an error message saying "something's missing, check your internet connection", where you can only click 'retry', not cancel or something, therefore making it impossible to switch servers to login to another world, because that error popup comes back immediately, sitting in the way of the login screen to try to login elsewhere.)
Anyway, EN1 doesn't seem to be having the server issue btw, so it's really only the US servers that are affected.