The reason MMT works so well for the US and allows for us to believe that deficits don’t matter, is that we only borrow in dollars. So long as we never borrow in other currencies, the system will likely keep working. Well, at least so long as the US dollar remains the world’s reserve currency because that creates a global appetite for dollars that allows for us to sell our debt.
The US will never retire its public debt. It will always and ever be refinanced at different rates and maturities. The goal is not to have zero deficits or to ever bring the debt to zero. This also works because we borrow only in dollars and we are the world’s reserve currency.
Still, it all does push to prickly questions about taxation. If the government doesn’t really need more than a third of my income in order to pay for roads, fix bridges and buy bombs, shouldn’t it give my money back?