Jamie Dimon has warned a default would cause a "cascading catastrophe of unbelievable proportions and damage America for 100 years"

 This so-called X-date should be viewed as a best guess by Treasury, not a set-in-stone deadline based on exact science. In other words, America could hit the debt ceiling days before, or days after, October 18.

There are many, many moving pieces here. Yellen herself warned the X-date "can unpredictably shift forward or backward."

And given the stakes — Jamie Dimon has warned a default would cause a "cascading catastrophe of unbelievable proportions and damage America for 100 years" — it would be risky for Congress to get too close to the X-date, let alone beyond it.

end partial quote from:

https://www.cnn.com/2021/10/01/economy/debt-ceiling-next-steps/index.html

Because of this it is theoretically possible that the U.S. and world economy could collapse anytime after today because of this uncertainty of when this stuff hits the fan. So, the world economy could theoretically collapse in a series of cascades in unpredictable ways any day now so basically the world economy (at least as it has been since World War II) might be ending any given moment now.

This will be true until the Debt Ceiling is raised or some other mechanism is created to prevent this inevitable debacle soon.