AWS CloudFormation StackSets announces the ability to deploy CloudFormation Stacks to multiple AWS regions in parallel. This reduces the overall stack set provisioning times and provides a performance improvement when using StackSets. StackSets extend the functionality of stacks by enabling you to create, update, or delete stacks across multiple AWS accounts and regions with a single operation. Currently, using StackSets you can specify the region order preference to deploy stacks across AWS regions in a sequential manner. StackSets now expands on that by providing the additional ability to specify deploying across AWS regions in parallel as part of the deployment preferences for the stack set.
Source:: Amazon AWS