Based upon my understanding of Modern Monetary Theory (MMT), it's proponents argue that when done correctly, the overabundance in supply will tap into suppressed demand and the insatiable foreign demand for the USD ensure any price instability will be transitory, especially when the excess USD is invested into technology and infrastructure to boost productivity and causes deflation.
I disagree with MMT’s “if you build it, they will come” mentality because it will only work if productivity continues to rise to act as a counterbalance to the increase of supply which is not guaranteed. In reality, productivity growth is hard to achieve as US productivity growth has been on the decline since the mid-2000s and staying below 2.5% since the 1970s.
Moreover, the US having reserve currency status means very little because the USD is no longer on the Gold Standard and most major currencies are no longer pegged to the USD. Global Reserve status simply means that other countries accept and hold the USD more than other currency which makes it less volatile and risky. However, the very reason why other countries hold onto USDs is because of the presumption of it being is a safe haven from risk and volatility. Therefore, it is foolish to expect that foreign demand to persist when the currency’s value is being quickly depreciated by money printing. Any stimulus provided by MMT will be temporary as easy credit will be quickly priced into the market and will require more and more to achieve the intended affected while causing massive psychological damage to the USD’s creditability.
Foreign central banks aren’t the ones buying the new T-bills