Followers of Christ should submit to earthly authority regardless of their approval or disapproval of the particular regime in power at the moment. Romans 13 was, after all, written during the reign of Nero, one of the most brutal anti-Christian rulers perhaps in all of history. Still, Paul encouraged Christians to pay their taxes, obey the law, etc. (Notice that Paul mentioned nothing about submitting to the law forbidding spreading Christianity itself.)
Believers should neither withdraw from society, nor mount some political "Jesus revolution" and establish a strict theocracy. We are given the unique privilege of choosing our leaders in the United States. I believe we should use that privilege to the glory of God.
I think the "evangelical establishment" (as I call it) has sort of fallen into this erroneous notion that America was once a Christian nation and that's been stolen from us by atheists and agnostics and secular humanists and all the "other" religious groups. We feel that it's our God-ordained duty to take back what we had and "put down" the rebellion of anyone who dares to challenge the sovereignty of this America-Kingdom of God hybrid idea that we've created.
Listening to agnostics, atheists, and their ilk, often their biggest beef with "Christianity" is all the evil it has purported over the centuries in the name of "doing God's work." I'm not going to address the egregious and unavoidable errors in this argument here, but the point is this: these people are pissed off for a reason.
Christianity has long been the de facto "official" religion of Western civilization. This idea took root during the Holy Roman Empire, and continued as Rome's influence spread over the globe (ultimately via the British Empire in the modern age). The Inquisition, the Crusades, witch burnings, and other events in the development of Western Civilization and Christianity, in addition to the contemporary issues surrounding civil rights are points against Christianity in the mind of an atheist (or agnostic).
I think the problem through the ages is simply this: Christians, as a whole, have failed to abide by the Law of Love.
For example, the Federal Marriage Amendment is touted by many evangelicals as a critical issue in preserving America as the godly nation it was designed to be. I think that's a mistake. I think there are other solutions to that semantic puzzle that don't alienate homosexuals and those who support them. I think if it was up to me, I'd broaden whatever Federal incentives are currently provided to man-woman marriages to include every taxpayer, married or unmarried. I don't need the Federal government to legitimize my marriage or anyone else's. that way the wind is taken from the sails of the groups saying "what about us?" (Feel free to insert the slippery slope argument of your choice here.)
To bring this ramble full circle, I think we, as followers of Christ, should let God's Love be our guide in relating to the world. This should include choosing our leaders. We are so eager to throw our support to the person who promises us some little glimmer of hope that we'll be able to re-establish the "city on a hill" and put all these non-believers in their proper place. I don't think that's the proper way to "go into all the world and preach the gospel."
Believers need to stop playing political catch up, trying to hang on to the illusion that America was ordained by God so that we, God's children, can have our way all the time. I do believe that America is God-ordained, as are all earthly dominions. I think the onus is on us to embrace the freedoms we have to express the love and grace of God.
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As an epilogue, I'd like to mention my intense distaste for the abject fear that many believers seem to have for the notion of postmodernism. Postmodernism is the paradigm that follows modernism. Postmodernism's main "theme", if you will, is re-evaluating the constructs embraced during the modern age. Postmodernism is not the scourge of Christianity. Christianity was born in a social-religious climate much like our postmodernism. It grew at that time like it has never grown since, and I wonder sometimes whether Christians can get their heads out of the sand and forge ahead instead of pining for the aged modern paradigm.
... but that's another post, I think.