I am an American living in Indonesia at the moment.

A lot of this is complicated. The US, as the only superpower (financial, cultural, and military) is not just one country among many. What happens in the US affects every corner of the planet. I am living right now in Indonesia and I see that every day. There are other countries which this can be said for, but they all are oil exporters and their impact is solely a function of those oil exports.

At the same time, I find a lot of Americans seem to think the other countries don't matter as much as they do. Consequently we have these bizarre discussions of how anti-American one country or another is, and, absent them calling America the great Satan or the like, one wonders how much of it is being intolerant of a level of dissent in foreign countries that would be perfectly allowed at home.

So the truth is very often more complicated than simple dichotomies.

The exception is that I would agree with #4. The US has a number of huge looming challenges which affect our country in a way no other country is affected. These include what I call "peak oil" (see below, not quite what peak oil theorists mean), the baby boomer retirement (this affects us differently than China or Japan, but Europe is going to feel the effects too), and a need to repair/replace much of our existing infrastructure. The infrastructure disrepair is becoming evident now, but I want to spend more time on the others.

Peak oil is usually defined as an absolute peak in production, after which production cannot rise to the same level. This is not what I mean. Instead I mean peak production relative to demand. We passed this peak in 1973 and after the oil crisis, oil supply never continued to grow in the way it grew prior to 1973. The crisis itself may have been political and the peak may be economic, but that doesn't make it any less real. Since 1973, oil production has gone up and down, but never continued to grow steadily as it had in the past.

Oil makes our economy work because it is a cheap source of energy. Unconventional hydrocarbons can help there, but they take much more energy to extract, and thus when energy is the limiting principle of your economy (and thus the primary cost), these are only profitable at high oil prices. Unconventional hydrocarbons thus act as a cushion against the sort of drastic decline we might see if we were only looking at light sweet crude. They are not a perfect substitute. And so I predict that oil production to the extent it increases, will not do so as fast as demand, and thus energy prices will continue to rise. The key driver of this demand is economic development in China, Brazil, India, and other countries. And thus any increase in production will not cause a collapse in oil or energy prices. Also note that most renewable energy has a comparatively low energy return on investment and so they are only really profitable when oil prices are high also, so they too act as a cushion. A transition from stored solar energy (fossil fuels) to current solar energy will not be economically pleasant.

The problem here is that higher energy prices, particularly oil prices, puts the brakes on all aspects of the economy and the US is particularly vulnerable. The US may already be past peak oil consumption as oil consumption has been falling off in recent years (how much is due to the Great Recession is hard to know however).

Retirement also affects different places differently. Europe and the US are likely to be hardest hit by the baby boom retiring, but the US is particularly vulnerable. In most countries in the world, retirement is not expected to be independent. When you retire, you move in with your kids, and help them raise their kids. They pay for your medical bills, and feed you, and you help them out as you can. In Europe and the US this is different. The expectation that we will have independent retirement means we have to save up vast amounts of money for that, and we also have to have programs like Medicare to provide the costs for caring for the elderly. However, the US is uniquely bad at cost control. Our public sector pays more per capita on medical care than any other country in the world and that's just the public sector (Medicare, Medicaid, the VA, and state/federal gov. insurance pools). We can't control costs there and so the costs will be truly hard to bear. Entirely missing in the health care reform debate has been this incompetence of the federal government to control costs in any way.

The US has one significant advantage in all this but it is one that could go away suddenly and leave us stranded. The USD is the world's reserve currency. This means that the national debt can be eased by the US essentially printing money to get out of debt. However, if that changes, the US access to international credit will suddenly be very different and our debt will become difficult to sustain. Right now we are lucky because there are no real alternatives. The Euro was looking good for a while, but not anymore.....

tl; dr: The US has a number of significant and unique challenges which will erode our presence in the world over coming decades. How much erosion we suffer will depend on a lot of factors however.