Maybe so, but holding a hard line separation of church and state stance establishes a weak choke point that allows a people's spiritual enemies to establish first a religious structure, and then a physical beachhead in an overarching spiritual war the likes of which can potentially overcome the natives.

The only guard against this potentiality is a limitation on immigration that would prevent a nation's enemies from getting anywhere near close enough to do that kind of inside damage in the first place, but we've thrown that option out the window because exercising our God given right to self defense would be racist.