If I may . . .

Not really: it was founded on beliefs (equality, Natural Rights) that could be secular--or not, as the reference to God in the Declaration of Independence attests. From that day to this one people--including postmodernists--have confused 'secular' with 'rational'. A secular belief is no more rational than any sacral belief is. All beliefs are true (for the believer) knowledge of an immaterial kind adopted in some kind of extra-rational way.