As bad as America is, it's still the most righteuos country on earth from God's perspective. (Notwithstanding our many serious sins, what current country on earth deserves God's blessing more?) So here's how I think (just speculating) that God will "destroy" the USA...
What if there was a huge evangelical revival in America and many millions of Americans sincerely turn to Christ. What if there ws a revolt against our secular, materialistic, media-driven society, and Americans by the tens of millions gave their lives to Jesus...then... The Rapture!
Imagine 70 or 80-million Americans suddenly gone, and only the godless left behind. It would "destroy" America. Europe would be relatively "untouched" by the rapture. So would Asia and Russia and the Middle East. But America would be most depleted by the Rapture, and those left behind would not exactly be our "best and brightest".
It's admittedly a rose-colored scenario (just a speculation on my part), but not out of the question, and not our of keeping with God's nature. For all of our abortion and love of money and media, we are still the most sincerely Christian nation on earth.
I think you presume too much. This nation is filled with unrighteousness. I don't think that God is a great respecter or self-righteousness.