This article provides a great explanation of MMT:

https://www.abc.net.au/news/2020-07-17/what-is-modern-monetary-theory/12455806

The federal reserve does not wait for anyone to buy bonds. It digitally creates money to fund its operations. The US has been in a deficit for almost all of its existence. Where does it get the money to fund wars, etc?

What do you think would happen if the US tried to pay off its debt? Have any of the deficits had a major impact on the currency and inflation? Could it be possible economic deficit theories are wrong and/or why do you believe they are a concern? We can't compare the US economy to countries like Venezuela, Argentina, etc. because they are vastly different than the US.

For another example look at Japan's deficit. The theory a country could default on its own currency and inflate it by creating more of it, is disproved by Japan's economic state. If I create my own money and owe it to myself, can I bankrupt myself?