How are national governments financed?

Basically, the general population is convinced by a minority that it is morally justified to hand over their currency to them in exchange for claims of the solving of perceived social problems. It is generally accepted that if you do not hand over your currency to this minority, that you should face coercion until you either do so or are forced into imprisonment.

National governments also finance themselves through debt. They basically make the promise to benefit society in a way that allows them to pay back the borrowed currency within a relatively reasonable amount of time.

For instance, as of this writing, the US national debt sits at around 16 to 17 trillion dollars. In fact, most of the currency gained from US citizens doesn't even go to expected social systems. It just goes to pay the interest on the debt accrued.