Which solution meets these requirements?
Change the AWS CloudFormation templates for us-east-1 and us-west-1 to use an AWS AMI. Relaunch the stack for both Regions.
Copy the custom AMI from us-east-1 to us-west-1. Update the AWS CloudFormation template for us-west-1 to refer to AMI ID for the copied AMI. Relaunch the stack.
Build the custom AMI in us-west-1. Create a new AWS CloudFormation template to launch the stack in us-west-1 with the new AMI ID.
Manually deploy the application outside AWS CloudFormation in us-west-1.
Explanations:
Changing the AWS CloudFormation templates to use an AWS AMI does not address the issue of the custom AMI being region-specific. This would not resolve the error related to the AMI ID not existing in the target region.
Copying the custom AMI from us-east-1 to us-west-1 and updating the CloudFormation template to refer to the copied AMI ID is the correct solution. This ensures the AMI is available in the target region with minimal operational overhead.
Building a new custom AMI in us-west-1 would require more effort and is unnecessary. Copying the existing AMI is a simpler and more efficient approach. A new CloudFormation template is also not needed if the existing template can be adjusted.
Manually deploying the application outside of CloudFormation would introduce more operational overhead, as it defeats the purpose of using CloudFormation to manage infrastructure. It is also inconsistent with automation best practices.
I rate that the answer is:
Copy the custom AMI from us-east-1 to us-west-1. Update the AWS CloudFormation template for us-west-1 to refer to AMI ID for the copied AMI. Relaunch the stack.