“...render unto God what is God’s, and unto Caesar what is Caesar’s...”
The tread is about thinking morally. We are not ruled by Caesar. We have a Constitution based upon “We the people of the United States...”
Christ’s Church extends to every aspect of our lives not just those buildings that we enter on Sunday.
So that only applied to the Roman Empire of Christ's day, and hasn't had any meaning since Caesar died.
Carry on.