National budgets are complicated. Part of that is revenue from interest on debt issuance. Another part is borrowing to make up for deficits. If all debtors stop

National budgets are complicated. Part of that is revenue from interest on debt issuance. Another part is borrowing to make up for deficits. If all debtors stop paying, revenue has to be adjusted by the expected rate of return - this is not equal, even if the amounts borrowed are. In turn, creditors will stop buying debt if they cannot make a return on interest: that means either spending has to be reduced by the debtor nation, taxes have to go up, or money printing has to begin. In cases like the EU countries that gave up their sovereign currency, printing is not an option. It's not as simple as canceling out all the credits and debits. Flows matter.