justme wrote:
Why have most currencies devalued against the US dollar with our debt at $19T.
Because the US is the premier government and economy in the world. In times of uncertainty, the US is the ultimate safe haven. Our national debt is not the same as you owing on a credit card. First, much of our national debt is owed to ourselves. The largest holder of treasury debt is the Federal Reserve.
Those countries holding US debt have a vested interest in keeping the US and the Dollar afloat. They become defacto supporters of the US when they hold Treasury bills. They have no interest in the value of those investments falling.
US debt is always denominated in US dollars. We don't owe gold, oil, or Rubles. If there was some sort of worldwide catastrophe and all the creditors of the US demanded instant payment, we could just turn on the printing press and send them stacks of paper. Ultimately, US currency is only legal tender in the United States. All that money those nations could in theory possess can only be used to purchase goods and services in the US. Since we are a net exporter of primarily technology and renewable goods (agriculture) even a run on everything US wouldn't create lasting damage to the country because everything we sell that can be exported can either be replaced (grains, beef, etc) or really exists only in theory (technology is 99% intellectual property, take the software, but the intelligence that created it remains to make the next generation). Things many foreign debt holders covet cannot be removed from the US (you can't buy land and buildings and then somehow take them to China, for example) so when they buy those items, they suddenly become vested in the US remaining strong, since you wouldn't buy a building hoping the nation it was located in would collapse into chaos.
Finally, since the US is also the most powerful nation on earth, those debt holding nations cannot do anything to collect that debt should they feel the need. This is probably unprecedented in history. Historically, poor, weak nations owed the big powerful nations and eventually those powerful nations either bled the weak ones dry, or invaded and took what they felt they were entitled to. That cannot happen in the US.