so the dollar is less about it's gold reserves, but more so about ALL reserves, from military, oil, gas, technology, open markets etc.
It is also based on the future production of goods and services; in other words, there is a premium on the dollar because the future labours of the US citizen will be used to repay the debt. It's a high labour class and product class too.
You're taking a dollar for the potential of a US worker to pay you back on that dollar that they borrowed from you
Does this make sense? Don't worry - it took our class a few good sessions to understand this concept too.