In general I agree with your predictions and most of your causes, however I believe you've fallen for the temptation to over-simply the situation.
Potential Mitigating Factors:
1. National Debt as a percentage of GNP is still far from setting any records. The question once we reach our real debt ceiling (wherever that is...) will we have created a more robust sustainable economy than we enjoy today.
2. There are lots of tools available which are capable of providing relief to the whole debt as a percentage of GNP challenge such as purposefully devaluing the dollar.
3. The dollar has value because we all believe it has value, as things get worse... people will still look to the United States as a relative safe haven for their wealth. The worse the world economy gets the more people invest in dollars.
4. The oil industry is a just enough, just in time industry. Changes in consumption patterns & production quantities can rapidly increase or decrease prices... much faster than consumption patterns or production can adapt to those changes. This means we will probably see several price spikes before we encounter permanent shortages of cheap oil. It looks to me like demand for oil is still falling faster than the oil industry is able to cut production.
5. Dollar deflation could significantly cut the real cost to extract oil from more difficult locations making cheap oil available for longer than expected.
Can we adapt our economy over the next 3-8 years to one that is capable of thriving with oil permanently over $100 a barrel? Can we bring exports and imports in line so that wealth is leaving the country as fast as it's coming in from other nations? Will Obama and the Democratic congress be aggressive enough to avoid a complete collapse?
We need to rely less on goods (especially food) that travels thousands of miles to get to the consumer. We need more renewable energy, if not before the next big spike, at least before the last one. We need a better trained, better educated, more flexable workforce and our system needs to be restructured so that manufacturing in the US is competative with manufacturing anywhere in the world. That means national health care and a tax code that rewards creating jobs and keeping them in the United States.
I hate to break it you you, but the country is already ruined, and Obama had nothing to do with it. Actually, liberalism and conservatism as they are practiced in America also had little to do with it. The biggest culprits are the same ones that have laid most of history's empires low: overspending, overconsumption, military adventurism, and believing that past prosperity is a guarantee of future prosperity as well.
The biggest long-term challenge America faces is the depletion of oil. Our very civilization is based on cheap oil, and cheap oil is virtually exhausted. We were in the early stages of a permanent oil shock when the economy collapsed, dropping demand for oil and temporarily "saving" us from runaway prices and shortages.
