How much is 1USD really worth? A very tough question to answer since the Nixon Shock of 1971, which totally decoupled the USD from the value of gold.
As already pointed out, billions of USD can be, and has been, created, seemingly out of thin air.
So, yes, a house of cards. Everything is fine until enough people stop drinking the Cool-Aid, start disbelieving, and topple the house of cards.
Here's a quote I managed to drag up and it sure seems that Paul Krugman might be clairvoyant (read last sentence) -
In 1996, Paul Krugman summarized the post-Nixon Shock era as follows:
"The current world monetary system assigns no special role to gold; indeed, the Federal Reserve is not obliged to tie the dollar to anything. It can print as much or as little money as it deems appropriate. There are powerful advantages to such an unconstrained system. Above all, the Fed is free to respond to actual or threatened recessions by pumping in money. To take only one example, that flexibility is the reason the stock market crash of 1987—which started out every bit as frightening as that of 1929—did not cause a slump in the real economy. While a freely floating national money has advantages, however, it also has risks. For one thing, it can create uncertainties for international traders and investors. Over the past five years, the dollar has been worth as much as 120 yen and as little as 80. The costs of this volatility are hard to measure (partly because sophisticated financial markets allow businesses to hedge much of that risk), but they must be significant. Furthermore, a system that leaves monetary managers free to do good also leaves them free to be irresponsible—and, in some countries, they have been quick to take the opportunity."