I mean, the government could run at a surplus and therefore not need to borrow money and start paying back the loans.

Its not really a ponzi scheme, but more that the US government has decided that it’d rather increase its debt rather than reduce spending.

As to OPs question. I think he’s referring to taxes and government benefits, but is discounting the fact that taxes are not the only source of money for the government, through bonds the government accrues debts that can exceed the amount collected in taxes.