When your debt is 40% then it costs you 2% of GDP to service your debt at 5% interest rates - this is traditionall the sort of level that developed economies have been pegged at. By contrast when your debt/GDP is 140% then you need interest rates to be 1.45% to keep your debt servicing costs below 2% of GDP. When rates start going higher then the numbers go south quite quickly.
It’s a given that higher interest rates would demolish the US economy. There’s also a case to be made that higher rates would feed upon themselves as investments in the US economy would get riskier and riskier as interest rates went up, causing investors to demand higher risk premiums, which cause higher interest rates. A scenario previously visited by Greece, Italy, and Argentina would ensue.
The question then, is whether the US government can prevent this outcome by keeping rates low indefinitely. So far, the Fed has been winning, and in the process building a huge war chest of assets that can be sold off on short notice to quash any idea of inflation. Investors say “don’t fight the Fed”. I bet the Fed will keep on winning at its new unofficial mandate to keep rates low.
Permanently low rates in the US set the stage for China or India to open their economies, float the world’s new reserve currencies, and capture a greater share of worldwide investment flows. Imagine if you could borrow USD for 2% and invest in the digital Yuan at a Chinese bank paying 5%. This would be the reverse story of how the US became so prosperous after WW2, wouldn’t it?
IDK if any other countries are actually in a position, politically, to capitalize on the opportunity, but it is there.