As I continue to think on the subjects of war and politics and biblical theology, I think I've come to this conclusion. The Old Covenant distinction between Israel and the nations is erased by the new covenant. As far as our understanding of salvation and the church this is relatively uncontroversial (though a few disagree entirely). But as far as the applicability of the whole of the Old Testament to modern life, I think there is a whole lot that could be said. Or, more honestly, many questions raised. The old covenant had a lot to say about politics. Does this now apply to the church (primarily? exclusively?) or to the various nations? Or does it apply to anyone or anything? It strikes me as odd that I've been thinking, on and off, about questions of the applicablility of the OT laws since I first read the theonomists back in college (and, to be sure some before that), but I don't feel especially closer to "the final answer".
My thinking right now is that the christian ruler (at any level and at any place) should simutaneously study the laws of Israel for wisdom about ruling, AND not identify with Israel as a special people/place/polity. This should also apply to the non-christian ruler, but they would be unlikely to listen to the church mostly.
As for the church, she should preach to the rulers and subjects faithfully from the whole of scripture, just as the prophets before. It is not up to the church to get results. It is up to the church to be faithful, and above all patient. Consider what Isaiah says to Egypt (30:15):
For this is what the master, the Lord, the sovereign king of Israel says:
“If you repented and patiently waited for me, you would be delivered;
if you calmly trusted in me you would find strength,
but you are unwilling." (NET bible)
We can preach to our nations and to each other and to ourselves. We just can't think that our nation is special in God's eyes, at least not any more than the next nation. I suppose I need to study Isaiah further on these things.