Edit: Ah, I see: only Conquest and Cultural victory were enabled in your game. But then I don't understand: "Cultural" means both, 20K and 100K, doesn't it? So why did the Americans not win via 100K before you won by 20K???
The AI never attacked you. Did you have to pay them a lot to keep them polite?
I noticed you played with "accelerated production". Do you think that on Sid level this makes the AI even stronger (after all they now need only 20% of everything...!) or does it favor the human player, because the AI has so much "overrun" that a lot of the production goes waste anyway, while the human can avoid it with better MM?
The Americans had over 170.000 culture in the end. So in a "normal" game they would have won an 80K before you would have been able to reach 20K. Do you think a 20K in a game like this is possible with all victory conditions enabled? Did you disable any other VC except the 80K (100K) victory?
I find it interesting that you played on continents. If I were trying OCC 20k on Sid, I'd play archipelago with few opponents, to try to keep the tech pace slow and choke the AI with unit support. (This is how I managed my 20k Sid HOF win.)
Frankly, for OCC I'd look for an island small enough that I could put a unit on each tile with coastal access, but I'm nervous about wars.
Wow! That is quite the game!
Gutsy call for certain to open with The Colossus. I guess that's possible on a small map, I'm rather surprised that you managed to go that long without a warrior (and still complete trades with the AI!).
BTW, what is the meaning of "OCC" and "HOF"? I am from non-English-speaking country so I do not know much of the abbreviated usage in the Cilvilization game. Are there some links summarizing these abbreviations?