>>1
What is a space fountain?
>>6
It is not impossible for the west to maintain the status quo without further expansion. That's the whole point of conservation. The sun outputs a ton of energy; if we can harvest a larger portion of it, we'd be set. I make no claim that doing so is easy; I'm only claiming that it's not impossible.
You forgot to mention that space exploration takes a LOT of energy. We don't know yet if it takes less energy to harvest asteroids or to refine low quality ores. You also forgot to consider risks associated with harvesting asteroids. A calculational error may send that asteroid into Moscow, instead of staying in orbit for you to harvest the minerals. I don't think Moscow will be very forgiving of your calculational errors.
The disease of financial greed is what caused all of imperial expansion in the last ~2000 years. Colonialism was all about exploiting natural resources in another locale.