Because money is a commodity that is openly traded around the world and through a variety of financial instruments, schemes and gimmicks -- some of them very, very exotic. So, how much a dollar is worth on the international market will be reflected on the price tag for that can of chicken and rice soup on the supermarket shelf.
That is certainly the reality, but have you asked why?
Chicken and rice soup, along with many/most goods are still domesticaly produced. Many are/more could be.
Does this central banking make Americans richer or poorer?
Let's focus on the central question of the battle between Hamilton and Jefferson.
The world has changed, for sure, but in the eternal battle since Christ with the money changers in the temple has not.