If AWS fully decentralized its control planes, they’d essentially be duplicating the cost structure of running multiple independent clouds and I understand that is why they don't however as long as AWS is reliant upon us-east-1 to function, they have not achieved what they claim to me. A single point of failure for IAM? Nah, no thanks.
Every AWS “global” service be it IAM, STS, CloudFormation, CloudFront, Route 53, Organizations, they all have deep ties to control systems originally built only in us-east-1/n. va.
That's poor design, after all these years. They've had time to fix this.
Until AWS fully decouples the control plane from us-east-1, the entire platform has a global dependency. Even if your data plane is fine, you still rely on IAM and STS for authentication and maybe Route 53 for DNS or failover CloudFormation or ECS for orchestration...
If any of those choke because us-east-1’s internal control systems are degraded, you’re fucked. That’s not true regional independence.