Use this filter configuration:
-> Root: /content/project/en_us/global
-> Rules: exclude: .*
include: ^/content/project/en_us/global/[a-z]{3}/jcr:content$
-> Reason:
The regex in Package Manager must match the complete JCR path. By excluding everything first, only the paths defined in the include rule are added. This include pattern captures only the homepage jcr:content nodes for each three-letter country folder, so it works automatically for all countries.
If country code length is different, use this instead:
include: ^/content/project/en_us/global/[^/]+/jcr:content$