Solution

Linux kernel , Linux distro & OpenBSD
Linux kernel is open source and its code can be viewed. many people download it, and it is seen by many professionals around the globe, so creating and hiding back doors inside the Kernel can be difficult.
Still there are reports that some people approached Linux vendors and Linux distro vendors to provide back doors and they deny their involvement in NSA.
Case is same for OpenBSD

http://falkvinge.net/2013/11/17/nsa-asked-linus-torvalds-to-install-backdoors-into-gnulinux/

http://news.cnet.com/8301-31921_3-20025767-281.html

What a country can do?

It is not possible to change all the devices country wide neither it is possbile to change Closed source products with Open source products at once nation wide, mostly people have no idea of Linux/Open source.

 To resolve this issue governments can follow these steps:

1. In any country all the technical people should shift to open source products first and learn how to use them.
2. Once technical people have shifted than Non-technical people should shift and they can get help from technical people.
3. As a result mostly people will get a good idea of Open Source products and in the mean time governments should prepare their own OS for their people.
4. Governments should not only built OS but a program to Update BIOS so that any infection present in BIOS can be removed.
5. In case hardware infections are present than governments will have to start making their own hardware for devices.

Governments can earn good money if they start making their own hardware.