One thing secular nations have alot less of is sectarian conflict. However our constitution still guarantees the freedom of religion - still justifies religious belief somewhat. This introduces the seed of social discord, because people then think that their erroneous beliefs are right, and other people's erroneous beliefs are wrong. Therein arises the "sectarian" divisions within a nation.

But we do have national security. We are not "sitting on the brink" of civil war because of religion. Science is common ground for everyone. It gives us the rational capacity to distinguish between fact and fantasy, and prevents us from starting armed conflicts based on personal beliefs that we know might be wrong. In fact if anyone pushes the point, they can quickly be argued down on the basis of rational arguments and scientific evidence. Secularism removes the endorsement of political authority and makes religious beliefs a personal choice. Without leadership support, fanatics cannot cause nearly as much trouble. Thus....

Science --> Secularism --> National Security