The Hebrew for "great" in Job 12:23 is not moral greatness. It is size, strength or power. The word assumes moral greatness only when used in reference to God, and it is in its only other OT appearance which is also in Job (where the word exalted appears in reference to God).
Thus. KJV says "he increaseth the nations...", or makes them grow. This is consistent with Psalm 75:7, Daniel 2:21 and even Acts 17:26.
There is no inherent greatness in any nation. Greatness is not goodness. Deuteronomy 4:5-7 recognizes "great nations", but Israel alone was deemed "wise and understanding" by other nations -- great ones that were not like Israel--only to the extent Israel kept and did the law. So, great nations that did not have the law would look at the great nation that had the law of God and say "they are wise and have understanding".
America is not good. Oh, it is great. But, it is not good. It is better, comparatively speaking, than a lot of other nations, and maybe all of them, but that just -- at best -- reserves a particular place in line for the last great carbon footprint, right?
Let's forget about greatness. Let's be holy, peculiar, showing forth the praises of Him who called us out of darkness and into His marvellous light. Let's find our entirety of being in the person of Jesus. This nation will melt with all the others and the whole of all of them won't be a penny weight in the measuring cup of God.