It's Christian in the sense that the overwhelming majority of citizens are Christian, which obviously is not the same as having an official state religion. Europe having just escaped a couple centuries of sectarian violence and America being settled by (among others) religious dissidents of a couple dozen sects from a dozen nations, one can see why the Founding Fathers had the good sense to make us aggressively non-sectarian, with no possible state religion. But that doesn't change the fact that the USA was formed by Christians. In fact, the earliest federal literacy programs were the distribution of free Bibles. With the rise of the progressives and humanists, unfortunately freedom OF religion has been morphed into freedom FROM religion.