The US dollar is not the world's "reserve" currency because of responsibility on behalf of the monetary authorities. Instead, the dollar's "strength" wages from the USA's self-appointed role as the world's protector.
Why does money have value? Typical economists claim that money is valuable because the government declares it so. But that is impossible, given the true origins of money, which are best explained by Austrian economists.
Logical positivism holds that theory is irrelevant to the empirical results. It is the other way around; One cannot understand or interpret economic data until one has a working economic theory in place.