Not every can be a pacifist-yet-some-how-a-conquering-GOD you know! I can't handle that much conquest, even with no stability. I can't get the vassals, and always lag behind in tech. I am also completely ******** at espionage, so I cheat a little...
BTW, I played as France to conquer Spain, it was much harder than you said. I had to race against Portugal to get all the independents after I finally conquered, lost, and reconquered Spain in a matter of 3 turns. They eventually popped back up in 1600 (Which got me mad, because I was stable, and Maya didn't pop up, nor Babylon, Carthage, China, Inca, or Egypt. So I made Spain mine again with a little help from world builder).
Anyway I was in an early 'world war'. It didn't take place in the Pacific or Asia, but the main battle fields were in Africa, North America, and Europe.
There was 3 mini blocks:
1:
France- Mexico, Spain (3 cities), Algeria
Rome- Libya (2 Cities)
Netherlands- Denmark, New York, Southeast Africa (2 cities)
2:
Russia
Germany
3: Only between me and Britain
Britain- Halifax, Guiana (Georgetown), Cape Town, Florida, Guinna (Bathurst)
Mali (vassal)
This is basically the seven years war.
I was preparing for war with Britain to take Guinna, Halifax, and to destroy Savanna to place New Orleans, and hopefully get Mali as a vassal.. Rome was unstable and was my ally. Germany and Russia declare war on my block and I was Afraid Rome would fall, making me unstable, but he built the Taj Mahol in time for a quick pick me up. I got my troops who were going to invade Britain's colonies in place, and declared war on them, knowing that Rome and the Dutch would be my buffer from the East. Within two turns, I got what I wanted and settled Louisiana.
The Dutch and the Germans were going back and forth in Denmark, so I sent two cannons to aid them. The Germans were scattering into Rome, so I went in with 4 musketeers and wounded them, killing my own (better then Rome falling IMO. I then sent in four cannons just as the Russians were coming in a wave of 6. I drove them back, killing four of their units.
Rome made peace with Germany and Russia right after that. Soon, me and Germany. Then Netherlands and Germany, status quo, with Denmark back and fourth at least three times. After I defeated a Russian wave or 8 in my mainland, the war was over, and I made piece with Britain.
The ending move of the Anglo-Frankish War was when my curassier in Orleans hit a musketman, a settler, and a worker when Britain tried to resettle Savanna on the ruins. If I could have redone it, I would have waited one turn and taken New Savanna. then I would have gotten maybe Guiana instead of 200 gold.
After peace was made, the Roman Golden age ended (which I had not known about) and they collapsed. I raised the city in the Alps (had Chichen Itza and Spiral minaret), and then took Rome. I thought Greece would fall first though, but they got a city in Sicily and Popeii. I destroyed the two citied in Libya.
Now a new thread remains: A Russian-German-Ottoman alliance and Britain now got Scandinavia as a vassal. I soon want to declare war on Britain again though. This time to raise Belize, the Guiana, and capture Capetown for the Dutch. This time, I want to get Mali as my vassals though.
I don't know who I can add to my posse, maybe Portugal, but I tell you how the next, real world war goes.
)
, then Spain collapses 
how in hell didn't you collapsed?
