The New Testament depicts church and state as separate entities (Matt. 22:17-21) — both of which are accountable to the One who has been given “all authority…in heaven and on earth” by the Father (Matt 
The New Testament depicts church and state as separate entities (Matt. 22:17-21) — both of which are accountable to the One who has been given “all authority…in heaven and on earth” by the Father (Matt 28:18). Not only is Jesus the “head of the church” (Eph. 1:22; Col. 1:18), but as the book of Revelation points out, He is also the “ruler of the kings of the earth” (Rev 1:5). Therefore, both church and state must respect God’s authority, upholding Righteousness and Justice in the process. Failure to do so results in the removal of the candlestick for the church (Rev. 2:5) and the rod of iron for the nation (Rev. 12:5). Although it is true that under the Old Testament the kingdom of Israel was a theocracy (or blend of church and state), under the New Testament there is to be a separation of these two entities.
The role of the church under Christ is presented as one of spiritual warfare (2 Cor. 10:3-5). On the other hand, Caesar (i.e., the state or civil government) is given a physical sword (viz., the penalty of death) to aid in its physical warfare against evildoers (Rom. 13:4). Unlike Israel of old, the church today is not in the business of taking human life. This is, however, the prerogative of the state (Rom. 13:1-7). But in doing so, the state is not free to arbitrarily and capriciously exercise itself, but must do so consistent with the principle of Righteousness and Justice taught in the Bible. The government is, therefore, duty bound to protect the law-abiding and punish the evildoers. If a government consistently fails to meet its obligation “under God,” which would be evidence it had become a Revelation 13 government, then there can be no real Justice. Under such a government, the law-abiding become the prey of not just evildoers, but the government itself. When this happens, such a government, along with its society, experiences the fiery wrath of the Lord’s righteous indignation (i.e., His judgment).
Christians are to be praying for the government so that it will meet its obligation to maintain order in the society (1 Tim. 2:1-2). In addition, they will dutifully pay their taxes to support the government, and they will always be found obeying the laws of the land as long as such do not breach God’s word. But, and this is most important, the government has no authority to tell the church what to do in spiritual matters. It cannot “under God” tell the church when, or when not, to pray; when to preach or not to preach; when to worship or not to worship. In these matters, the church takes its orders only from Christ, not government. In purely secular matters, the church is obligated to respect and obey the laws of the land. This, however, is the extent of the state’s authority and the church’s obligation to obey. If, and when, the state seeks to dictate to the church spiritually, the church is obligated to engage in holy disobedience (cf. Acts 5:29).
On the other hand, the church, as “the pillar and ground of the truth” (1 Tim. 3:15) is obligated to preach the truth whenever, wherever, and to whomever it applies. It must do so without respect of persons. This may involve telling Caesar he is wrong on some moral or spiritual issue. The Truth must always be preached without fear or favor (i.e., not “having men’s persons in admiration because of advantage” [Jude 16]). So although the state is separate from the church, both of these entities have roles to play “under God” — one spiritual, the other physical. As such, the state is no less accountable to the Lord’s principle of Righteousness and Justice than is the church. Truth is, the state is subject to Christ and will answer to His “rod of iron” if its policies are contrary to the Lord’s principles, and this is true whether the state likes it or not. In fact, the degree to which a government finds such things offensive is a good indicator of just how far down the path towards a Revelation 13 government it has traveled.
So, I said all that to say this: If Christians are not being salt and light, they are sinning, and these sins, if unrepented of, will not only damn their souls, but serve to place yet another nail in the nation’s coffin. Remember, “The wicked shall be turned into hell, and all the nations that forget God” (Psa. 9:17).