One of my favorite writers on Church/State issues, Douglas Farrow writes in Touchstone about The Audacity of the State, from which I quote a part:
. . .
The Erastianism which (to speak anachronistically) had long been trying to get the upper hand in Christendom, managed to do so in the wake of the Lutheran Reformation, though it was in England that it first succeeded. The year 1534 brought the Act of Succession, and a mandatory oath of allegiance that included assent to everything declared by parliament about marriage in general and about Henry’s in particular. Later that year, the Act of Supremacy also established the king’s ecclesiastical jurisdiction, making no mention of the proviso formerly attached to it by the bishops: “as far as the law of Christ allows.”
Christendom, of course, had already seen many princes who were determined to make the church do their bidding. But Henry, by writing his supremacy into the laws of the realm, inaugurated a new era. In that era, the ongoing process of subordinating religion to the demands of the state would outrun the monarchy as such, and the Church of England too. Not merely some, but all of the church’s authority over things public would gradually be expropriated, binding even the conscience—as the Act of Succession already did—to the authority of the state.
Today we live in a society that shrinks in horror from the very idea of established religion, something the American Constitution in any case forbids. Yet we live, even if we live in America, in states increasingly ready to withdraw conscience clauses not only from public servants but also from doctors and druggists and so forth, requiring them to violate the teachings of their religion and the dictates of their consciences in order to demonstrate their allegiance to the state.
In Britain, and increasingly in North America, even churches and charitable organizations are not exempted from laws that demand conformity to state-endorsed ideologies loaded with religious implications. Penalties for violation include heavy fines or even imprisonment. Thus have we come round to accepting Erastus’s invitation to the state to punish the sins of Christians, supplanting the church’s sacramental discipline. We have come round, that is, to the de-sacralization of the church and the re-sacralization of the state, which is once again taking a tyrannical turn. . . .