It does seem to be a networking issue. I have a ec2 instance in us-east-2 that is accessible through a "Global Accelerator" but not externally through my ISP.

It does seem to be a networking issue. I have a ec2 instance in us-east-2 that is accessible through a "Global Accelerator" but not externally through my ISP. That ec2 instance can talk to other ec2 instances that are on us-east-2 - but none of those other instances are accessible externally.