The outage apparently affected only a small number of Windows Phone 8.1 users. Unfortunately, the same connection to Microsoft's servers that allows Cortana to be updated twice a month, is also the personal assistant's downfall. If something happens to Microsoft's servers, down she goes.
Right now, Cortana is available only in the U.S., on Windows Phone 8.1. The only way to get the new build of Windows Phone in the U.S. is to sign up as a Windows Phone developer with Microsoft, or by purchasing the Nokia Lumia 635. The latter comes with the new build out of the box. The Lumia 635 can be pre-ordered now from HSN, bundled with a pair of chargers for $119.95. The device will ship on July 21st.