cat region_loop.sh 
#!/bin/bash

REGIONS=('us-east-1' 'us-east-2' 'us-west-1' 'us-west-2' 'eu-west-1' 'eu-west-2')

for REGION in "${REGIONS[@]}"; do
  echo "${REGION}"
done

$ ./region_loop.sh 
us-east-1
us-east-2
us-west-1
us-west-2
eu-west-1
eu-west-2