Google clearly states that duplicate content within a single, or multiple, domains is not advised. This is understood, but I am not sure of any exceptions for sites with region-specific content that is often replicated across locales.

For example, a site's /en-us/about page could be identical to /en-uk/about, whereas most likely /en-ja/about is unique.

Are GYM smart enough to understand that the initial URL depth is a locale specifier? Is there any robots.txt or header, etc, trickery that I should include to outline the site's international structure?