Hi Sriram,
the country grouping is not an attribute of orgunits.
However, if you assign company codes to orgunits the company codes determine the country grouping.
As company codes are only assigned at the top of their structures, this should be an easy exercise, if you have less than 50 company codes.
Should you still need to select your structure by company code, then you can do so by building a little infoset containing orgunits incl. the org assignment infotype, so you can use it as a selection field in the query.
cheers
Sven