Amazon AppStream 2.0 is now available in the AWS GovCloud (US-West) Region, an isolated AWS Region designed to host sensitive data and regulated workloads in the cloud for customers who have U.S. federal, state, or local government compliance requirements. With this launch, Amazon AppStream 2.0 is now available in nine AWS Regions. For a list of regions where AppStream 2.0 is available, see the AWS Region Table. You can deploy general purpose, compute-optimized, memory-optimized, and graphics-pro streaming instances in the AWS GovCloud (US-West) Region to meet the needs of your users. Graphics-design instances are not available at this time.  

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/10/amazon-appstream-2-now-available-in-aws-govcloud-us-west-region/