When the U.S. was on the gold standard, other governments could demand payment in gold. Under the regime of the French President Charles de Gaulle up to 1970, France reduced its dollar reserves, trading them for gold from the U.S. government, thereby reducing US economic influence abroad. This led to President Richard Nixon eliminating the gold standard in 1971.
As of today, it is reported that the U.S. has Official US Gold holdings = 8,133.5 tonnes or 260,272,000 ounces. See: http://en.wikipedia.org/wiki/Official_gold_reserves Of that, 147.3 million ounces are held at Fort Knox. See: http://www.usmint.gov/about_the_mint/fun_facts/index.cfm?flash=no&action=fun_facts13 I suspect the balance is held in New York.
The U.S. debt held by Major Foreign Holders is $3,076,900,000,000 ($3.0769 Trillion) See: http://www.treas.gov/tic/mfh.txt
If we were under the gold standard today, our gold would be valued by Foreign Holders of Debt as follows:
$3,076,900,000,000 divided by 260,272,000 ounces = $11,821.86
As U.S. Dollars continue to get created at breakneck speed, this disparity will be addressed by the marketplace. Will a 200 year currency defy a 5,000 year currency? You be the judge.