The reason we obey authority is because none of it exist apart from God. He is the one who establishes and maintains it. This is entirely different from saying no authority exists that does not reject God or his Word. It does not mean all authority is Godly. Even most of the kings of Israel were not Godly. Most of the Jews saw this and were looking for a Messiah-Revolutionary. Jesus disappointed the Jews because he failed to end Roman oppression and build his kingdom right away. They were wrong in assuming that this is what he came for. Instead, he turned out to be a model citizen. If you were hoping for an overthrow of the government, you were seriously let down. This in large measure led to his execution.