When each country will have their own OS, 1. NSA won't be able to ask Microsoft to use their master key to spy on people of other countries. They will have to find a way to do that.

2. Policy wise people of each country will enjoy their own privacy and security. Their security won't have to rely on the US senate approval.

3. OS build by each country will work like virtual regional borders for their people. It will be the responsibility of the developers of respective countries on how they manage the security and privacy of their own OS. So, their would be a competitive advantage for public in general.

4. Economically, a lot of required technical work will create more job opportunities. Governments and local businesses will get to bite the share of big, centralized companies.