How to override default aws region credentials for Terraform?
I believe you would be using multiple modules to create various resources(EC2,ELB, Etc) in AWS using Terraform. You can create a custom module having output value of each variable you want to configure per your requirement like aws-region, etc.

Then source(import) this custom module into your resource module and use its values using $.

custom_module

output "aws_region" {
  value = "us-xyz-1"
}
output "aws_anyproperty" {
  value = "abc"
}

Add above custom_module as source in your resource module

module "custom_module" {
  source="../../../modules/custom_module"
}

provider "aws" {
  version="~&gt; y.x"
  profile="${module.custom_module.aws_anyproperty}"
  region="${module.custom_module.aws_region}"
}