Some schools of economics say that the Gov. is not at all like a person [= human or corp.] so the Gov. should not act like a person; other schools will claim that they are the same so the Gov. should act like a person.
I am not an economist and it has been a while since I read what MMT had to say on the subject, so I might get some points wrong. I also add some of my own creation.
The Gov. is not like a person because they [Gov. vs persons] are different in several very important ways.
1] People die and Gov. *can* live forever.
. . a] When Gov. do end the creditors often lose their principal. But this may not be for hundreds of years.
. . b] When people die the next generation usually is raised and can go on on its own.
. . c] Persons amass assets, these can be liquidated to pay off the dead's loans. The Gov. doesn't amass assets and liquidating what it has at some point would be stupid.
. . d]
2] Persons get income by working *outside* the family (or corp.) unit. Transactions inside the family unit don't count as income or expenditures. OTOH, the Gov. gets its income by taxing [i.e. taking] money from persons *inside* the nation [here I'm equating the family to the nation].
. . a] The US Gov. gets little if any income [taxes, fees, etc.] from other govs. or persons outside the nation.
. . b] *All* of a family's expenditures are made *outside* the family unit; most the the Gov.'s expenditures are made *inside* the nation.
. . c] So, when a person borrows from an outsider and spends the money outside the family, the family now has a thing which is not as valuable as what was spent for it or the family has nothing (if it ate food or went on vacation); the cash spent is still cash somewhere. OTOH, when the Gov. borrows money from an American and spends it inside the nation, it is totally different from what the person did. The lender still has an asset equal in value to the loan [the bond or T-bill] and the person who got the cash also now has the cash.
. . d] When a person spends money the money leaves the family unit, then the Gov. spends money it mostly stays inside the nation. When a person borrows money it must borrow from an outsider this brings money into the family unit, when the US Gov. borrows it usually borrows from an American or US Corp., so this doesn't bring money into the nation.
3] All persons [even the largest corps.] are nowhere near as big and don't have near the impact on the economy that the US Gov. does.
4] A person earns income by making transactions with other outside persons, OTOH the Gov. gets its income mostly from taxes which it just takes from persons [people and corps.] inside the nation.
. . a] I have no objection to this taking. It is how govs. have always gotten money to spend. In the Bible, King David uses taxes to pay for stuff. Under feudalism the King usually got a lot of money from the land that he owned. Under Capitalism the Gov. should not own the means of production to earn money to aviod the need for taxes.
. . b] Compare what happens with the Gov. borrowing money to spend or the Gov. taking money to spend. When the Gov. borrows the lender still has an asset, the bond or T-bill. He can sell it to get cash at any time. There is plenty of cash around so any bond holder can always sell his bond for what it is really worth.
. . When the Gov. takes money with taxes, the taxpayer gets nothing in return, except for his part of the value of the benefit for what the Gov. spends its money on [everything it spends money on].
. . When a person *earns* income both parties to the transaction get some value directly from the transaction.
. . Taking (= taxing) is quite different from *earning* because the taxpayer gets nothing *directly* from the transaction.
5] The Gov. is not a person. It should have no will of its own. It should be ruled by the people. I should be a "Gov. of the people, by the people and for the people."
In all these ways the US Gov. is different from persons in economically *important* ways and this is why advice that is good for a person is not good for the Gov. and vice versa.
Some schools of economics see this. Other schools say they don't see it, but they seem to me to be creatures of the rich to and say what is good for the rich to the detriment of the mass of the people.