Probably decades, though I can't predict the future. I can only look at historical examples. Power of civil services are decreasing, while military power is increasing. The trouble is, so few people truly understand the nature of our very strange and complicated empire that our own government does not even acknowledge its existence. It will take a very bloody world war to take down the US--empires traditionally fall after a war, not simply from economic implosion. We still have troops stationed all over the world and still hold considerable leverage in most places. We've lost part of South America and we are fighting politically to regain control of Tunisia, Libya, and Egypt. We've already abandoned our old Syrian buddies and are waiting to buy off the next regime that takes over there. We have Afghanistan and Iraq as invasion points from which to strike at Iran next. Although it's true that financial ruin is upon us, I think this will only be the catalyst for dictatorial emergency measures similiar to Germany in the 1920s and 1930s. Even if the US went bankrupt, we still have enough nuclear weapons to wipe out the planet.