It wasn't just an US outage, it was a worldwide issue. Europe seemed to be less affected by it than other parts but it was worldwide.
I simply do not understand the reason for not allowing offline saves. I understand they might be trying to stop people from creating modded saves as done in other games but there are ways to stop that from happening, like automatically checking the integrity of the save by creating a checksum system which compares the offline save with the last online save and once verified updating the online status. For further discouragement of hacking they could also just permanently ban any accounts which are found to have tampered with their offline save file, easy and far more convenient than expecting everyone to have internet connection everytime they choose to play.