As a normal person, if your income is $3k every month and you spend $4k every month, you go bankrupt eventually.

The insight of modern monetary theory is that rule does not apply to government, when debt is in the money issued by that government.

The national debt does not represent a number that must someday be repaid. It can be rolled over indefinitely, by issuing more bonds. In the US monetary system, the government can issue bonds not money. New money is issued by the central bank, the Federal Reserve.

When the Federal Reserve inflates the monetary supply, some/most of that new money goes to the financial industry. The rest goes to the government. Deficit spending is just the government claiming its fair share of the newly created money.

Why can't the government just print and spend money instead of borrowing it from a central bank? The rules of the financial system were written that way, by lobbyists from the financial system. With access to unlimited capital, they have an unlimited lobbying budget. It's impossible to change it now.

The national debt is merely a running tally of money stolen by the government via inflation. It cannot every be repaid. It's built into the rules of the monetary system. If the government tried to jack up taxes and collect enough money to repay the national debt, it would cause a deflationary spiral of the monetary system.

In a system of debt-based money, money is created when it is borrowed and destroyed when a loan is repaid. To avoid hyperdeflation in a recession, deficit spending by the government is needed.

It doesn't have to be that way. It's enforced by various treaties, that countries have to have a corrupt monetary system like the USA. Any country who tried to hold out against this system would have its leaders couped out of a job.

It's even worse in the EU. Since no single country controls the Euro, it's possible for EU countries to actually go bankrupt. They can't endlessly inflate their way out of debt, because the EU rules impose government debt limits.