As part of the American Constitution the federal government is not permitted to establish an official governmental religion to thereby be imposed upon the population, yet, it does grant as a material right the free exercise of religion for each of its denizens. This, in a nutshell, demonstrates that this government understands well that a citizen's personal faith is their own choice, of which this government respects that, and further, that this government does not believe that as a government it should or shall impress upon its people its own orthodox view on religion.
This thus means that per its Constitution, the church and the state, are separated, by Constitutional law, and whether one is a believer in the importance of religion and faith or not, the fact that they are separated should be considered to be a very good and prudent thing. The reason that this is so is because when the governance of the state also controls the religion of that state, then effectively, the people are controlled from a material standpoint as well as from an ostensibly moral standpoint. In other words, when the church and state are united, those that are not believers in that particular orthodoxy, are stuck living within a construct in which they have no material sanctuary, as well as having no religious sanctuary, and therefore their personal choice and their personal beliefs when it comes to religion, are negated; as well as their being, depending upon the structure of that government, also limited in their opportunity for gainful employment and overall liberty.
So then, when the church and state are one, the people are, by definition, oppressed, for their opportunities for personal faith have been limited, and the limiting of those in regards to their faith, is a particular nefarious form of discrimination, for the relationship between each person in regards to their God and their beliefs, should be between them, their God, and their beliefs, all without undue interference. The reason though why the state so often has a compelling interest in their people's religious affairs and beliefs, is that all states, to a certain degree, fear their population being disloyal, and a population that has religious beliefs that may be inimical to the state, is a population that is always going to be harder to control, and consequently much harder to keep loyal to that state.
So too, many believers, are rightly concerned about their eternal destiny, so that when the state and religion are one, that type of governance, can impress upon their people, the standards that they expect from their people for the benefit of the state, in which, by meeting these particular standards, the people are instructed that they will thereby find great glory in the world to come. Unfortunately, when the state and religion are one, the orthodoxy of such, is often corrupted to benefit those that promulgate the rules and regulations of that state, often, to the ill effect of the people, in whole.
All of this basically means is that when the state desires to control the orthodox religious beliefs of its population, then that state has done their population a great disservice; for the greatest states are the ones that provide their people with the accouterments of liberty, free religious expression, and the fair pursuit of happiness, without the limitations of forceful state sanction imposed.