They can and do create money in support of the budget. They can’t create unlimited money without consequence but they do create money for the budget and money returned to the government via taxes is destroyed. The gov takes out loans by issuing bonds and the National debt is simply a running total of those issued bonds over time. The federal government doesn’t need anyone’s money to have money, they create the money, they tax it back to get rid of it. It’s a spend first tax after system.