I think it's a mistake to say the republic is the Biblically endorsed form of government (see Calvin on this here, especially section 8). There have been many faithful kings in the Bible and history who aren't to be despised for not changing to a republic. And any time we start saying "no other nation," there is a strong possibility we are giving too much credence to an earthly nation. Of course, we should be thankful for our great national heritage. But sometimes the rhetoric leaves one feeling like USA is the only safe or good place on earth, when it is the church in Christ that is the only safe place. Some nations are more rightoues than us on the issue of abortion and sodomy. Many nations now send missionaries to USA, and we need them. Rev 3:14-22 is for America.
Faith and politics; God and country
Our faith should be worked out in the political realm. There is a fine line to walk here. My concern is not to keep people out of politics, but to steer us away from placing faith in politics or in a form of government. God uses politics to accomplish His purposes, but He does this as a funnel gets oil into a car: the main thing is the quality of the oil, and the engine, not the funnel. The main thing is the righteousness and faithfulness of the church within the nation, not how much and how strongly the church voices and funnels its opinion into DC. Doing this makes DC the source of hope for change, when our hope should be the Spirit dwelling within us. Politics reflects culture, it doesn't shape it, and culture will only be transformed by winsome evangelism and faithful living, the Spirit regenerating hearts.