Matthew 22:20-21 New International Version
20 and he asked them, “Whose image is this? And whose inscription?”
21 “Caesar’s,” they replied.
Then he said to them, “So give back to Caesar what is Caesar’s, and to God what is God’s.”
It has been a long time since I was a math nerd. The A that I earned in Calculus in high school was the last math class that I ever needed, or wanted, to take. But I still enjoy a well laid out Venn Diagram's ability to explain the relationship between things that otherwise are confusing to people. In my World Religions seminar I created a three circle Veen Diagram to illustrate the overlap and differences between the terms: Jew, Judaism, and Israelite because people can belong to one, two, or all three of those categories.
When the Pharisees tried to trap Jesus between the power of the Roman Empire and man's higher obligation to God, Jesus could have given an answer that would have resoundingly supported both Jewish Nationalism in the 1st Century, and Christian Nationalism in the last two thousand years. But he didn't. Not at all, not a bit. Instead of ranking the obligations that we owe to God and earthly powers, Jesus differentiated between them.
The Pharisees were expecting Jesus to argue that "B is proper subset of A" (the circle within the circle in the chart above), either that God's rule is supreme, or Rome's, but they're all one circle. In a sense, that's true, God is indeed supreme over all, the entirety of the created universe belongs in a circle contained within the all-encompassing circle of God. But, and this is key, that's an ontological answer (i.e. the nature of reality), not a functional one. God chose to allow humanity a degree of freedom and autonomy, to let the governments of humanity exist without being theocracies directly under his immediate rule {Israel prior to their requests for a king come closest to that model}.
In the end, 'Christian' Nationalists want the two circles of human government and God's rule to perfectly overlap, to make them one in the same (i.e. one circle, not two). Jesus rejected this idea, he wasn't interested in conquering human governments, his Kingdom would be founded on different principles and pursue different goals. The Church of Jesus Christ must follow his lead. We are not called to triumph over Caesar, or even to be Caesar, but to continue to give to God what is God's.
What belongs to Caesar and what belongs to God? That's an important question, and one God-honoring men and women in the Church might not always agree upon, but one thing is certain, there is a distinction between them.