The New Covenant declares that because of the perfect sacrifice of Jesus on the cross "for the sins for the whole world" (1 John 2:2), "their sins and their iniquities will I remember no more" (Heb 8:12, 10:17).
It would also help to remember that even in the Old Testament, God would not judge Sodom until AFTER ONE MAN, righteous Lot, was no longer there. I think there's many more righteous per capita in America than there was in Sodom.