Starting today, Amazon Virtual Private Cloud (Amazon VPC) traffic mirroring will be available in both AWS GovCloud (US) Regions. AWS GovCloud (US) Regions are isolated cloud regions, designed to host sensitive data and regulated workloads for customers with U.S. federal, state, and local government compliance requirements.

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/09/announcing-amazon-vpc-traffic-mirroring-for-aws-govcloud-us-regions/