That is one monetary school of thought that I believe will remain valid as long as other nation's currencies are measured against our own, if that standard slipped though that debt would suddenly be realized and repayment would be required at a respectable rate to continue doing international business. It's a major problem I have with MMT - it assumes American prosperity in perpetuity, but history has established that perpetuity isn't a thing and those chickens will come home to roost... If we're smart then the US economy can fade gracefully, like England, otherwise it'll likely get violent and revolutionary.