The U.S. has no debt. It prints all the money it needs beyond what already exists. The bonds the Treasury sells into the private sector are, in effect, an interest paying form of money. When the Treasury sells a bond it is simply exchanging an interest paying form of money for a non-interest paying form. When the Treasury sells a bond, private sector bank reserves are debited in the equivalent amount and the Treasury's reserve account is credited with money previously printed and spent into the economy. Although the Treasury's selling of bonds appears to be "borrowing," in reality no money is actually borrowed. The transaction is merely an exchange of different "types" of money between the government and the private sector..
In the case of deficit spending, when the government acquires goods and services from the private sector, the Treasury overdrafts it's reserve account, and the fed covers the overdraft by "printing"; private sector reserve accounts are credited by the amount printed. By this mechanism, in effect, the private sector converts its productivity into new money (outside money). There is a net increase in the amount of private sector money (outside money).
When the government taxes the private sector, private sector reserve accounts are debited and the Treasury's reserve account is credited. The amount of money (outside money) in the private sector decreases.
In the case of non-deficit spending, when the government acquires goods and service from the private sector the private sector transfers goods and services to the government sector; the government's reserve account is debited; private sector reserve accounts are credited, and their is no net change in the amount of money (outside money) in the private sector, i.e., the transaction simply returns to the private sector money that was previously removed via taxation. .
N.B. -- "government" here means the U.S. government. Some countries do actually borrow, but not the U.S.
Good stuff. I am probably half-way to digesting this as viewing the Government outside the microeconomic view of "the firm" will make my monkey brain explode.