In it's entire history I'm not aware of the dollar ever collapsing in value.
Unlike 3rd world countries, the US has a very good track record in keeping the value of it's currency.
Yes, the dollar has a reasonable rate of inflation (unlike 3rd world countries) but that is not the same as a collapse in the currency.
___________________________________
Get 420 with bitcoins at zeltasgarden.com
The US dollar has lost around 95% of its purchasing power in the last 100 years.
In the 70's its value also dropped significantly with the rampant increase in inflation, I believe the value dropped around 60-70% for a short period.
But to add my 2 satoshis to the thread, the US dollar is primarily backed by trust.
It is trusted that the US will remain stable and not veer to far off the monetary course, that it will operate with the best interests of the economy at heart. Since WW2, the US has taken on the role of the global policeman. Yes, this role, at the most basic level, is reinforced by the size and capability of its army. It also used to be due to its industry although that landscape has changed significantly. The same cannot be said about other countries.
No one doubts the ability of the US to deal with any 'threats' to US dominance (also a part of 'trust'). Invasion of land for ideology (Vietnam) or resources (Iraq)has been a favourite but increasingly the wars being fought are economic (Venezuela, Iran).
Similarly, looking at the Sino / Japanese conflict over a small rocky outcrop in between the two: not so much about the damned rocks, more about economics and power. The real war being fought now is a currency war. The Japanese have abandoned the rest of Asia in a way and killed the Yen. This affects the export markets of China, Korea etc, so there is a lot of military flexing and posturing going on.