[akira2501]

> I've talked about this before, but the US debt feels to me mostly like an accounting mechanism.

That's because that is precisely what it is. Here's the ledger[0].

> What I mean is that the US government is mostly in debt to itself, in money it can print.

The debt is already purchased. The government is in debt to securities holders. Several government agencies have purchased these instruments, but they only represent about 25% of the total holdings.

> Anyway, I really don't understand if and why the US National Debt matters that much (I'm not saying it doesn't, I just don't get it)

When there's a large differential, it means some part of your government accounting is not balanced. There can be good reasons for this, but given the size, continual growth, and no apparent strategy it remains concerning.

[0]: https://fiscaldata.treasury.gov/datasets/monthly-statement-p...