As you say, money can be created out of thin air. The money that the USA spend in a moment in time is limited by the real resources available (overspending would create inflation) [1].
The 'national debt' in only a number reflecting pass spending and has very little relevance. The USA dollar as the currency of 'the empire' have a special status, but that it's not what protect the USA of default, but the strength of the real economy and being the issuer of their own currency.
I think that article misses out on a couple of points:
1) Central banks do have the ability to control monetary supply. This is exactly what quantitative easing is -- the fed purchasing securities with funny money to drive the price of things up and spur artificial inflation and call the resultant increase in market prices 'growth.' That article was written before we started going far off the deep end with monetary policy.
2) Modern monetary policy is based around faith. If people have faith in a currency, it has value. When that faith wavers, the currency is worth less than the paper its printed on. As an amusing (but not necessarily relevant) aside that's already the case in the US coinage, where we've had to pass laws prohibiting the melting of coins as the metal is now in many cases worth more than the amount of money they're supposed to represent! The entire purpose of pretending the money has intrinsic value is not some holdover from the gold era, but to try to convince everybody the money has intrinsic value.
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The real reason the USD has remained so powerful is because it guarantees access to oil and oil remains the most valued resource in existence. And so holding onto USD ensures you have are indirectly holding onto access to oil, which has value everywhere. Iraq, Iran, Venezuela, Syria -- these nations all have one thing in common. They expressed intent to no longer peg their oil prices on the dollar and to start trading primarily in different currencies. Haven't you ever wondered how arbitrary our Mideast relations must seem until you consider this? Or why we 'waste' trillions of dollars to no apparent end in these nations?
Because what we're doing in the Mideast is very much intentional. We're best buds with Saudi Arabia - one of the most oppressive regimes in existence and a huge sponsor, and source, of terror. For instance 15 of the 19 hijackers in 9/11 were Saudi. But all that matters is that Saudi Arabia plays its role of an obedient lapdog when it comes to the petrodollar - so we're best friends forever. If they ever indicated genuine plans to move away from the USD, expect for us to suddenly realize they're not a great country and urgently decide we need to 'bring democracy' to them.
As you say, money can be created out of thin air. The money that the USA spend in a moment in time is limited by the real resources available (overspending would create inflation) [1].
The 'national debt' in only a number reflecting pass spending and has very little relevance. The USA dollar as the currency of 'the empire' have a special status, but that it's not what protect the USA of default, but the strength of the real economy and being the issuer of their own currency.
[1] - http://hir.harvard.edu/article/?a=2853