Money relies on the retention of belief of value. Without this a currency sinks. All the world is engaged in make-believe and financiers and creators of stock understand this.

China realizes the US currency income floated their own fixed currency for a long time. By returning our dollars and keeping their factories busy, their national wealth increases because the rest of the world respects the dollar and its power. Machinery, textiles and the finished products of industry can be bought with ease and enrich their lives. At the same time the people become skilled and each persons wealth and QOL increase.

If I told you the US prints up money as needed and never accounts for it, would you believe me? And if you did would you tell anyone? How do you think others would react to this knowledge, and would folks suspend disbelief? Removal from the gold standard made possible currency production at an enormous scale and was done to pay for the Vietnam war.

Since we do not have accountants from other nations watching us 24/7 as we print money they have to take our word on how much we produce and what it's "real" value is. Each nation is in the same boat.