  Blandus Rex asked, after my last post on Leviitcus and Jeremiah, "[Do] Christians (true decendants of Abraham) [have a responsibility] to fear God's judgement on their lands if they do not strive to obey His (at least Moral/Ethical) law? " or "Is there some scripture honoring belief by Christians that could say, "Hey look at how serious God was about these kinds of things for the people-group He had a special relationship with. If He was that serious with his chosen people, how much more serious will He be on 'all the nations? ' America had better repent! " I see this as two questions, requiring two answers. Christians do claim to be the spiritual heirs of ancient Israel, thus whatever God said to the ancient Israelites is certainly applicable to modern Christians, though modified by the New Testament covenant and by the modern situation (the fact that, as I pointed out earlier, there is no covenantal relationship between God and country anymore). Certainly God's dealings with ancient Israel are instructive in understanding God. Knowing how He reacts to those who hold His laws in contempt should make Christians that much more careful and serious about their commitment to the cause of Christ. For the relationship between modern nations like America and God, however, I think the parallel is not to ancient Israel but to the ancient pagan lands around Israel. What is important is not that Moab, Philistia, Edom, etc. were pagan, but that they were nations which God had not made a specific covenant with. God did judge each of these nations, just as He did Israel and Judah, but not on the same standard. If I recall my minor prophets correctly, He condemned Moab not so much for worshipping Molech, but for worshipping Molech with infant sacrifice. The other scripture which is instructive on this point to me is God's comment to Abraham, that He would give Canaan to Abraham's descendants, but not yet, because the iniquity of the Ammonite was not yet complete.
I read that to mean that God did hold the Ammonites to a standard, but not to a covenantal standard. I think He judged the Ammonites on the standard of Romans 1: natural law, the things that everyone naturally knows is right and wrong. The Ammonites were wicked, to be sure, but it would require 400 more years before God was ready to destroy them. So, yes, God does judge nations. Christians can work to influence their fellow citizens to act in ways that don't antagonize God.
And certainly, Christians can draw lessons from God's dealings with ancient people, including the Israelites. However, I think Christians have two loyalties. The first is to God, and thus the first and most important question to a Christian is: God was serious with His chosen people in ancient times---am I being serious before Him? The second loyalty is to their country. I care deeply about my country, very very deeply. But on another level, it's only a temporary thing.
I'll be here for at most another 60 or 70 years, and it isn't likely that anything I do will greatly influence my people one way or another. When I'm dead, America will continue on, although hopefully I'll have done more good than harm. Given that, though, what I do for God is much more important than what I do, or even worry about, for America. 
