First, a difference in trade is not a debt. A debt is something owed. A trade difference is simply that: a trade difference.
And there are advantages as well as disadvantages to trade "imbalances". Much of the trade differences exist due to causes beyond the borders of the US. Primarily fixed and quasi-fixed exchange rates. A trade deficit essentially means that capital is flowing toward the US. Has been for a long time. Always does when a country is doing well. The better it does, the wider the gap will become.
Fundamentally, the trade deficit is due to everyday America citizens buying more foreign goods than foreign citizens buying our goods. To ask the government to have a hand in changing that is asking for trouble. What could they do?
Well, for one they could place import tarrifs to raise the proce of imported goods. Not a good idea on the whole, but it would curtail import spending. Or would it?
The US is becoming more and more a service exporter. but you don't see fearmongers talking about the surplus in exports of services, no sir. Why? Well despite the tempest in a teacup about offshoring, we maintain a growing surplus in that area. At current growth rates it should offset entirely the goods import in about a decade. The numbers you refer to in the trade deficit only mention goods, they exclude services.
Also, a certain amount of economic power comes with having such a trade imbalance. Woe to countries that offend the American buying public when the buying public realizes what they have.
Further, this goods trade imbalance is a funding the development of higher order economies elsewhere. Even in the failing economies of Europe. As foreign economies develop, they will they will require additional service industries. As it always is, they will largely import these services. And the US is placed in prime position as it is currently and forseeably stands to provide those services. Indeed, it is the US trade imbalance that is supportign the world economy. That's why countries in Asia are desirous of keeping the exchange rates the way they are. They are not competitive in a free flowing exchange rate.
This is why the single largest thing the US FedGov could due to alter the imbalance is to make the foreign goods more expensive by enacting higher and higher tarrifs or other cost increasing mandates. Of course, I am opposed to that.
This is also why any "fall" would be a boon for America, and a problem for the rest of the world. Americans would turn that voracious appetite inward when the costs are similar or better. This would cause a massive "influx" of investment, new companies, and job growth. Keep in mind that Americas productivity is much, much higher than that of Europe, China, and even Japan. We can move quickly.
On the subject of who holds the debt:
Currently, the two largest owners of US Government debt are Japan and China is quite false, and demonstrably so. Perhaps you could show some sources?
The US Public debt is held in two categories. One is public holdings, the other is government holdings. Yes, US government; I don't mean foreign governments (or even state/local).
Of the two the ratio is about 4.4/3.1 public(inlcuding foreign government)/domestic government. This tells us immediately that the largest single holder would be US government --though that should cause concern to stir in people as well. Yes, the government owes itself; nearly half of the debt in fact. I'll let you all stew on that for a moment or two.
Next comes everyone else. Of that 4.4, only 3.9 is marketable. Of that 3.9 the largest share is 2.1 held as notes. Notes can and do change hands frequently and have maximum terms of 10 years (2,5, and 10 IIRC). The idea that a given country holds a substantial part of that is often claimed, bit rarely if ever substantitated. It also begs the question of what difference it'd make.
So what if Japan or China, or even Iran held say half of the t-notes? What can they do with them? They can sell them. They can hold them until they are redeemed and then either cash out or reinvest. Where's the problem? Sell off of bonds? Another so what is coming.
First, some perspective. Only about 551 Billion dollars of the public debt is through federal bonds. Out of 7.7 trillion that is what about 6.5%? We get bond sell-offs quite frequently. last year long bonds saw, IIRC, a roughly 25% above norm selloff rate. It was taken in stride w/o any rises in interest rates.
So of that 551 Billion (As of Nov 22) in bonds, just how much do you think is held by Japan and China? Much of bond investment is actually done in bond mutual funds, and as such is institutionalized and spreads risk over the various bond types. This minimizes selloff effects. And remember, if someone sold a bond, someone else bought it. And nobody is going to buy it at a loss, even if the seller is taking a loss to sell it.
But what if a rise in interest rates as a result? Bear in mind that four years ago (federal funds rate) interest rates were at 6.5%, compared to 1% last year and 2% this year. If rates doubled next year ans then doubled AGAIN the year after we'd be above where we were 4 years ago. How likely is that? Not very.
So in effect, your Japan/China owns and would sell off bonds causing inflation elephant is in fact, a boogeyman.
Now let us talk about the debt as a "record high". Is this a problem? In a way, yes but not the way you and most pundits talk about. It is a problem solely in that it is a representation of lost productivity due to government expenditures over private ones. Each dollar taxed is about $1.60 removed from the economy after conservative cascade effects are calculated.
Now, let us return to the record numbers claim. Again here it is a matter of scaremongering. First, let me state that as a libertarian, I'd like to see the government carry no debt other than times of full-scale war.
That said, the debt is not as bad as it is made out to be. I'll illustrate simply. Let us say I carry a personal debt of 100K. Is this a problem? Maybe. It is if I make 20K/year and this is non-collateralized debt (i.e. credit cards, etc.).
However, if I make 200K/year, this debt is certaily not an issue, especially if it is a loan on my 175K house.
The point? Perspective, again. How much is the budget defecit (indeed the budget) as relates to the GDP/GNP? your figure states 3.6%. Let's go with that. Nah, lets round it to 4%.
Now, is that a problem? We can look to history to see prior rates. Looking at history we see deficit rates upwards of 10, 15, even 20%. Thus taken in that perspective we are not at record highs.
The claim of bigger and bigger as raw numbers is without merit in a growing system. As it is not a zero sum game, numbers must be made relative to have any potential comparison merit.
So the budget deficit is itself perhaps not an elephant. It is an issue, but only due to excessive government spending. Sadly, it is found easier to raise taxes than to lower spending. An elephant? Maybe a baby one at best. Is it one that will cause massive problems? Sadly, no.
As to the US Dollar as an elephant, you pretty much eliminated it as being one yourself. The fact is, as you stated, changes in global currency domination are very slow to occur. IIRC, each time it has happened it happened at a time that the dominating country was weaker than any opposing currencies.
On the oil front, there is a somewhat silent move underway. The transportation industry is already moving to an alternate fuel source, though the one it is may suprise many: Ethanol/Gasoline.
This combination is the single most powerful move being made in the US right now. While we are the alrgest oil consumer, we are also one of the largest oil producers, let us not forget. Why does that matter? For many reasons, only a few of which I'll talk about here.
First, as the largest consumer (by far), small shifts downward in consumption can have far reaching effects. Argentina has shown this on a smaller scale. They've switch to an average 20% ethanol use, and IIRC, cut their oil use by more than half.
Since E85 blends (85% ethanol, 15% gasoline) displace imported oil at a rate of 7 to 1 (i.e. one gallon of ethanol displaces 7 gallons of gasoline), you can begin to see the effects are truly dramatic.
E85 is a technology alredy in place in nearly 4 million cars and trucks on the road in the US today. Unlike dreaming of a mythical hydrogen replacement, E85 is working today. I run it in my Suburban. With the MPG I get of fuel, I (well my wife actually, I drive my Vette most of the time, and she drives the burb) am less dependent on foreign oil than a Prius. My Suburban is fueled 100% by "native" fuel. Why? Do the math. I burn through gasoline at a rate of about 90+MPG. And it is cheaper than the gas I run in the Vette.
That little sidebar is important. It represents one half of the change that will make oil importation actually turn into a declining rate. Ford, DC, and GM are making these engines standard on an increasing amount of vehicles. (And they are better for the air to.) This is important for a couple reasons. One, it will erode the "danger" of a switch to Euros in the oil market. Two, it will lower importation of oil, thus lowering the trade defecit. With the move to E85 usage and the next technology I'll mention we could be fully independent oil-wise inside of 15 years.
The second half of that equation is TCP, and I don't mean Transmission Control Protocol. We have the capability to make oil. With the current prices, we can make it cost competitive even on the low startup scale. Extremely conservative estimates put our capcity to produce light crude at a rate exceeding our current demand by about a factor of 3. Using half of our agricultural waste we can produce our current demand w/o pumping a drop from the ground or importing a single barrel.
Turning this tech on urban refuse would supply another 1.5X our current demand. Couple this with E85's spreading use and it is not hard to see a real transition not only in our lifetimes, but in the next two decades (if not sooner).
Right now, the government sits on this bit of information. Let Russia, Saudi Arabia, etc. actually start trading in Euros, and watch the government start pushing this tech combination. First by requiring it as new vehicle standards, and second as a product of the EPA and cleanup fields.
This technology has a fast ramp-up time as it is stable, well tested and rather simple.
With the US capable of withdrawing from the oil market as a major demand source, what oil is traded in is less and less important. Thus the Dollars is a boogeyman as well.
Most of what you talk about that could be a genuine issue, is not in the hands of the US government. Foreign governments using fixed/quasi-fixed exchange rates. Consumer spending. These are the greatest opportunities to prevent the probability you mention. Neither of which are in the purview of the US government.
In closing, I find it odd for someone to say that the speculation they just provided is unlikely, and then say that it "won't go away" if ignored. Indeed, I posit that just the opposite is the case. If the government tries to meddle more than it already does, it will precipitate a failure. The high price of oil (which is purely speculation driven at this point) is providing the means to eliminate many of the (unlikely) potentials you list.
When the government gets involved, debt goes up. So if you beleive it a problem, keep the government out of it. That will solve the rest of it. The mentality of "the government can fix it" is the source of at least two of your so-called elephants.