A couple of points... I hadn't thought about it this way before, but I saw someone pointing out that the primary point of "separation of church and state" is to make it clear that the President of the US is not also the arch-bishop of the country. That the bishop of Virginia doesn't have an automatic Senate seat. Etc. We're not even close to that level of entanglement.
Lower-level stuff, like nativity scenes on public property, I tend to think should be handled democratically and locally. There'd be lots of different demarcation points across blue and red states -- displays agreed to by the people who are going to be seeing them. One of the things that ticks me off is that so many of these stories seem to be in reaction to lawsuits, which means public policy is being made by a very small minority.
As to whether America is a "Christian country" -- well, depends on how you define it
We do not have an official American Christian church (thank the founding fathers!). And we've been blessed by contributions from all sorts of religions/cultures/etc, which I certainly want to see continued -- that's one of the things about America I'm very proud of. But when somewhere around 90% of the population describes itself as Christian, and when so much of our culture comes from a Christian background (including the concept of separation of church and state, btw -- Jesus was specific about his followers also being tax-paying, law-abiding Roman subjects/citizens, regardless of the official Roman theology. There's nothing like that in Islam) ... well, I think as a generalization, "Christian country" works pretty well. In the same general way that Pakistan is Muslim, India is Hindu, France is secular, etc.
PJ
