AWS IAM is having issues again
Wherever possible, don't use us-east-1. It's one of the older regions and parts are aging. Yes, I know there are things that are only available in the old regions but most services are globally available. I've worked with a few ex AWS SWEs and SREs. They drink the kool-aid and won't say anything bad about us-east-1 but they also won't launch net-new services there. YMMV