THANK YOU EVERYBODY THAT SENT IN A TRACEROUTE.
We were able to identify the issue down to the Hurricane Electric and Telia transit providers. We turned off those providers and all traffic is now routing over alternate unaffected routes - i.e. everybody should be back online at this point.
Understand due to the nature of this issue it is possible there will be further downtime/connectivity issues as there is no way for me to predict what changes have to be made to fully resolve the issue. Turning off these transit providers is a band-aid over the symptoms and not a solution to the problem. The goal was to bring everybody back online as quickly as possible.
We couldn't have isolated this issue without the traceroutes - thank you.
That said - if you are still experiencing connectivity issues do please email maintenance@ with a traceroute.