That was an answer to a trick question. The inquisitor was trying to get him to admit to defying Roman rules so he could get him imprisoned. And he gave an answer that the coins that have Roman emperor faces on them belong to the emperor, implying people could stop using those coins.
Even the most generous pro-government take on that passage would have him believing that the state should be separate from the church, so church doctrine should not be imposed through state decree.
Did the historical Jesus really say that? He wasn't one of the religious authorities who had a deal with Rome. Many Jews didn't like Roman occupation as seen by the revolts. If Jesus had issues with the Jewish authorities, he probably did with the Roman ones as well. Apocalyptic Jews would have believed God was coming soon to overthrow the kingdoms of the world, which were controlled by evil spirts.
