...Give us an example of a successful, self-sustaining secular nation with reasonable longevity.
I asked for the modification of "secular" to "non-Christian" because I assumed you were not in favor of American schools promoting the worship of sun-gods and such. If you would like American schools to allow teachers to promote religions other than Christianity, then I will discuss that. I was not trying to weasel out of anything by changing secular to non-Christian.
My point is that there have been dozens of large, "successful, self-sustaining secular[non-Christian] nation[s] with reasonable longevity". I consider a thousand years to be a reasonable definition of longevity.
So what's your point. There is no one particular belief system required to sustain a nation or culture.
And this is not a particularly troubled or devisive time in America's history. We have been through much worse.