Buffet is disengenious

Buffett says the U.S. will not “have a debt crisis of any kind as long as we keep issuing our notes in our own currency.” Inflation resulting from a “printing press” approach, however, is a serious threat. Pragmatic Capitalism

He expresses what he knows to be a tautology and passes it off as certain wisdom.

The fatal error is in the thing called, 'Our own currency'. Out in the periphery, we might just have a different currency, that is someone else's. Here is how Zimbabwe handled it:

The use of foreign currencies were legalised in January 2009, causing general consumer prices to stabilise again after years of hyperinflation and price speculation.[50] The move led to a sharp drop in the usage of the Zimbabwean dollar, as hyperinflation rendered even the highest denominations worthless.

People who currently use the old Zimbabwe dollar are not having a debt crisis, but they only trade in wallpaper.

Argentina is a serial defaulter using their own currency. Iceland defaulted. Part of Europe are defaulting, and Europe uses its own currency. The US engaged in gold defaults during the great depression. Two years ago California went through a partial default, issuing laser print money in the place of dollar debt to government contractors. California is likely to do it again.

MMT miss one point, we reach a point in which it takes too many policemen to chase down the alternative currencies.