You speak of fluctuations - you should perhaps speak of crashes of demolition derbies as economies crash into each other outside the USA they destroy ours in the process. The Chinese are the biggest holders of our outstanding debt and we would not be able to service our debt, not even pay the interest on it, so our own economy would crash.
When there is nobody to whom to export our goods, nor because they ceased to manufacture for lack of cashflow, anyone to sell us goods we need, what do you think happens? To our economy?
You describe a chicken or the egg situation but it is more likely, since the value of the dollar is artificially kept high by being the sole currency with which to buy oil, that if it is unlinked from oil, the crash will arise insidethe USA and our crash will bring down everyone else. With China clearly at the forefront.