To use a terrible analogy that doesn't hold up under close scrutiny but is sufficiently accurate to answer your question:
Just because you spend more than you earn using your credit card doesn't mean you don't have money in the bank. You can also use your credit card to put cash in your bank account.
The US doesn't hand people treasury bonds to pay them. It uses treasury bonds to put money in its treasury. Then it pays its operating expenses out of the treasury. If the treasure runs down to zero, it can't pay any of its expenses, but it will almost certainly never run down to zero. It gets in new revenues all the time (even without borrowing). Just not enough to meet all of its expenses.
The US doesn't hand people treasury bonds to pay them. It uses treasury bonds to put money in its treasury. Then it pays its operating expenses out of the treasury. If the treasure runs down to zero, it can't pay any of its expenses, but it will almost certainly never run down to zero. It gets in new revenues all the time (even without borrowing). Just not enough to meet all of its expenses.