Modern Monetary Theory is the new thing among progressives. But it's been tried by many others, including the Roman dictators who ruined the Roman economy and had Rome falling apart before the barbarian invasions.
Throughout American history, politicians have incessantly awarded preferential policies (e.g., “corporate welfare”) to special interests that has allowed them to create monopolies dominating virtually every major market.
America's "defense" budget is really more than $1.2 trillion, more than double the Pentagon's official "base budget," once we include all the other related spending like that on "homeland security" and veterans affairs.
Just as unilateral free trade results in a more solid economy for the countries that adopt it — even within an international economy of protectionism in other countries — so would a commodity-money based economy surrounded by fiat-money economies.