well....first of all a limitation to *some clones only* isn't a wise decision because there are lots of cases where some clones do work, while the others don't.

Now to you question...if the country is somehow stored in meta information like the set description or name, you can easily filter the sets.

Scanner -> Scan Results ->Set Information Button brings you to a powerful window which allows you to enable/disable sets. The 'select sets' edit box (+ apply button) gives you -additionally to manual enabling/disabling sets- the chance to set sets by using regular expressions and variables.
For example entering "%d=*(japan)*" (without the quotes) enables all sets which got (japan) in the set description. Check out the documentation for further variable information. Also check if the parent/clone option is disabled because if enabled, the belonging parent/clones will be enabled as well.