will kafka clusters accepts iam role authentications from outside of aws?

Hi there, yes for IAM access control you can configure clients outside AWS as well. Here is the blog that talks about connecting from a client called Conduktor which is running outside AWS using IAM access control (1). Please use this as a reference. If you continue to run into issues, keep us posted with the error or the best way forward would be to open a Support case so that logs and other information can be looked at and proper guidance will be given.

(1) https://aws.amazon.com/blogs/big-data/securing-apache-kafka-is-easy-and-familiar-with-iam-access-control-for-amazon-msk/