Ireland owns about 0.1% of US securities debt ($0.28 trillion)[1]. That's a _very_ low circular factor.
[1] https://www.thebalance.com/who-owns-the-u-s-national-debt-33...
Also worth looking at the last time the USA completely paid off its government debt.
> On January 8, 1835, president Andrew Jackson paid off the entire national debt, the only time in U.S. history that has been accomplished. [1]
[1] https://en.wikipedia.org/wiki/History_of_the_United_States_p...
In Andrew Jackson's case they also raised taxes:
Which, in the long run, will also make the stock market, and their options increase, as revenue and profit inflate.
But not in the short term.
It's like they are mortgaging the White House at 0.25% and buying bonds that pay 4%.
The conception of federal debt as some giant anvil hanging over our heads is not correct. Foreign holdings only account for about a third of all obligations, which the US could—but will never, for obvious reasons—unilaterally take off its books and ask anyone who has an issue with it to take it up with the DoD.
This narrative, while often repeated, is nonsense.