First off, to restate, I’m in no way suggesting blind submission. I believe we need to take responsibility for whether we submit or not. My concern is that we don’t put the responsibility for our submission (or lack of) on the authority.
How is authority established? When does a usurper of authority become the new authority?
I don’t know the answer to all that. There are biblical examples of God-directed rebellion and of godless rebellion. How do we tell the difference today? I can explain parallel and hierarchical authorities invading each other or intervening to relieve injustice and suffering, but internal rebellion (of which there are biblical examples as well) is more of a problem. Whether Christians are take part or not, I suggest we are far to quick to say, “Yes”.
As for the US, I am no expert, being a NZer in Australia, but in general I’d suggest that every authority is under another, ending with God. If a lesser authority is willing to rebel against a higher authority, you can either shelter under the lesser, knowing he will face the heat, or refuse to submit, appealing to the higher authority.
As for the Constitution, it’s law, not authority. It has no authority without people in authority who exercise power to ensure people abide by it. Therefore, if someone opposes the US Constitution, you appeal to those authorities.