Aside from that, us-east-1 is the most critical region to loose for AWS as some services run solely there. So if AWS looses us-east-1 I expect some services not to function anymore globally, at least for a while. In contrast if they loose one of their more recent regions, let's say eu-central-1, I expect all other regions to continue to run as usual.
Another problem with loosing us-east-1 is that it's also the most frequented AWS region. So lot's of customers would shift their workloads to other AWS regions. While that could cause some stability problem due to unexpected spikes in usage they'd be probably just temporary. What's more relevent is when you look at available resources. Let's take EC2 as an example. I'm pretty certain that AWS doesn't have enough spare capacity in other regions than us-east-1 to satisfy all customers in case us-east-1 is suddenly not available anymore. And there starts the interesting part. For EC2 it's simple: customers with reserved instances first. For all other service it's probably: Most important customers first. So if you happen to be a not so important customer for AWS you might end up not able to run your infrastructure, simply because AWS has no capacity left to satisfy all customers. If in general all AWS regions would be equally utilized that probably wouldn't be a problem at all.
Contrary to popular myth, nukes don’t have a 30 mile blast radius.