Looking back on this post, I think you're right. A Nation is 'saved' if it has a mission from G-d, saved for the purpose for which it was made, and yet it seems to me that I can no longer discern what the National Mission is for the United States of America.
As Tertullian said; "What does Athens have to do with Jerusalem?", and America was built on humanistic and indeed 'Hellenistic' philosophy, man centered....
Israel is built on Jewishness, Serbia is built on "Serbian-ness,", and so on, but America just seems like a Gentile Neo-Pagan Philosophical Ideal to me. Not the Tribe of Judah or the other Tribes of Israel.