CloudFront availability via GovCloud

The following should help you.

https://docs.aws.amazon.com/govcloud-us/latest/UserGuide/setting-up-cloudfront.html

Setting Up Amazon CloudFront with Your AWS GovCloud (US) or Resources

Amazon CloudFront is a web service that uses a global network of edge locations to deliver content to end users with low latency and high data transfer speeds. CloudFront is an AWS global service that you can leverage with your AWS GovCloud (US) resources. Requests for your content are routed to the nearest edge location, so content is delivered with the best possible performance. CloudFront is optimized to work with other Amazon Web Services, like Amazon Simple Storage Service (Amazon S3), Amazon Elastic Compute Cloud (Amazon EC2), Elastic Load Balancing, and Amazon Route 53. CloudFront is not available in AWS GovCloud (US), but you can use CloudFront in the standard Regions and point to your AWS GovCloud (US) resources.

CloudFront also works seamlessly with any non-AWS origin server, which stores the original, definitive versions of your files. Due to the isolation of the AWS GovCloud (US) Regions, using CloudFront with your AWS GovCloud (US) resources is analogous to using CloudFront with a non-AWS origin server.