Our site with full local API continued to work ok. Even the topo basemap tiles. All other viewers dependent on js.arcgis.com CDN sites went down and arcg.is were http 500. Illustrating "in the cloud" is a double edged sword.
I recommend everyone in emergency management to always maintain a common operating picture web map viewer with the local API, server set to run all local with local SDE set up for disaster data and copy of all local relevant datasets. Ours continued to work perfectly. I was teaching a class on GIS today on AGOL; this was a teachable moment. We got a chuckle however of the long "snack" though.