Yeah I think there are a number of "hidden" dependencies on different regions, especially us-east-1. It's an artifact of it being AWS' largest region, etc.
us-east-2 does exist; it’s in Ohio. One major issue is a number of services have (had? Not sure if it’s still this way) a control plane in us-east-1, so if it goes down, so does a number of other services, regardless of their location.