Meh. We will just come up with a fix. Like the Trillion dollar coin. Obama almost enacted it which I am fine with. The fact is undeniable that we will hit your mark and you know what happens then? Not much. Business as usual after a selloff in the markets. It will quickly recover.The magic number is when the cost to service that debt becomes a big enough component of the federal budget (it's like 7% now) that critical services like the military or social security need to be curtailed because there's just not enough money. And if we borrow and borrow and borrow and our credit rating gets lowered, that debt service will go up significantly. Like any household/company, debt payments not related to increasing investment are an anchor on your overall potential.
https://en.wikipedia.org/wiki/Trillion_dollar_coin
https://www.forbes.com/sites/kotlikoff/2013/01/19/the-treasury-has-already-minted-two-trillion-dollar-coins/#1bd69f6a6994
Obama told the podcast that, amid the possibility of a government shutdown and default that would most likely have lowered the US's credit rating, the administration was considering numerous options to avoid the shutdown and deal with the national debt. One of the ideas floated, Obama said, was having the US Treasury mint a coin worth $1 trillion to pay off a good portion of the debt.