Sorry for going slightly off topic here, but i want to propose something a bit less obvious, but it came immediately to me after reading this and i feel it should be said in this topic.
my interpretation of the prediction:
"In the City of God there will be a great thunder,
-the city of god could be a term for the united states. this country is one of the most religious countries, considering how many christians there are and how much religious bias there is about god. A great thunder could easily be some major crisis or an arguably unjust war- 9/11, the iraq war, vietnam, pearl harbor, the civil war, etc.
Two brothers torn apart by Chaos,
- two brothers could represent countrymen of the united states-- democrats and republicans. they are obviously politically 'torn apart by chaos' by decisions made by the president and other issues, such as abortion.
while the fortress endures,
-here the fortress could either mean the world, or the united states again. if it was the united states this would enforce that the chaos the country is thrown into is simply political and not physical.
the great leader will succumb,
-the great leader = the president
The third big war will begin when the big city is burning"
-The third world war will begin when the united states is in chaos.