can we deploy the same pulumi stack with same state to different aws regions in the same aws account? or do we need to create a seprate stack and state backend for each region?

Is it part of the same "application"? If so, can you loop the creation of resources in the stack? List the regions in config and deploy the same resources to each region as part of that one stack

You can create resources in difference regions using manually-created providers. If you want to use only default providers, then you'll need to use different stacks. Generally, if this is "base" infrastructure and must exist in multiple regions, then a single "base" stack is suitable.

those are ecs containers with cloudmap service discovery and alb etc.