[dragonwriter]

> I think you may be confusing Western society with the US. It's not a tenet, fundamental or otherwise, of many Western societies

It's a fairly common element of Western societies, though the particular expression varies; ranging from broad tolerance despite a formally established religion through a firm secularism in the public square; the US, though it professes a reasonably strong though not extreme form that amounts to neutrality actually has fairly weak separation between privileged religious communities and government power in practice.