You need to notice here, currently, the web application is in us-ease-1, and the user base grows in the us-east-1 region. The very first step, provision multiple EC2 instances (web application servers) and configure an Application Load Balancer in us-west-1. Now, create Global Accelerator in AWS Global Accelerator which uses an endpoint group that includes the load balancer endpoints in both Regions.
Read this blog about AWS services to know more.