Unable to grant additional AWS roles the ability to interact with my cluster

You will want one of 3 things; either:

• assume the arn:aws:iam::123456789012:role/myAmazonEKSClusterRole in a terminal session such that the aws eks get-token run by kubectl will behave correctly
• create an awscli profile that assumes the arn:aws:iam::123456789012:role/myAmazonEKSClusterRole role and update the args: to include [..., "--profile", "whatever-you-call-that-profile",...]
• or assume the role in a terminal, run aws eks get-token, and put that static credential in your kubeconfig since it doesn't seem you need the credential for very long just to update that ConfigMap

For the first one, I mean aws sts assume-role --role-arn arn:aws:iam::123456789012:role/myAmazonEKSClusterRole ... | tee sts-creds.json and then export AWS_ACCESS_KEY_ID= AWS_SECRET_KEY= AWS_SESSION_TOKEN= based on the contents of that json

For the second one, I mean:

$ cat >> $HOME/.aws/config <<FOO
[profile my-cluster]
assume_role = arn:aws:iam::123456789012:role/myAmazonEKSClusterRole
source_profile = whatever
; or credential_source = whatever
FOO

according to this documentation