Along with that pronouncement, Jesus commanded Christians to be good citizens (render to Caesar the things that are Caesar’s), but he also — stunningly — indicated that the pagan state could be a legitimate form of government. The denarius in question not only bore Caesar’s image, but it said that Caesar was “God” — it was idolatrous and deeply offensive to the Jews. Yet Jesus instructed them to pay the poll tax, worth a day’s wages, even though it was a sign of subjugation to the ungodly Roman emperor.
Jesus was not in the theocracy business. He never instructed his followers to advance an earthly kingdom or impose Old Testament laws on the Roman government. He said, “My kingdom is not of this world” (John 18:36). Even though Jesus had “all authority in heaven and on earth,” (Matthew 28:18) he did not instruct his followers to set up an earthly government. Rather, Christians were to be citizens of the countries in which they lived — and were to be good, law-abiding citizens unless the law conflicted with their duty to God: “We must obey God rather than men” (Acts 5:29) when there was a conflict.
Augustine explained that Christians are pilgrims, caught in limbo between the City of God and the City of Man:
[T]wo cities have been formed by two loves: the earthly by the love of self, even to the contempt of God; the heavenly by the love of God, even to the contempt of self.