The President's job is to defend the Constitution, the document that creates our system of government with express limitations on its power over the citizens' rights.  His responsibility is to the country and the citizenry, not the rest of the world.  If Trump adopted a Christian platform, you'd be all over him like white on rice over his breach of the wall between church and state.  

Even Jesus expressed that government should be left to its own devices.  The Romans had one of the most violent governments in recorded history, but Jesus did little to protest them even as they crucified him unjustly at the behest of those who saw him as a threat to their own system of government.