What, if I (a European) decide not to buy American treasuries, a squad of Marines is going to bust my front door?
The only realistic options that exist at the moment are going back to the gold standard (not viable for most countries) or shifting to the yen (which is tied to the dollar as Japan is the largest holder of treasuries).
It will be more costly for the people doing this later, of course.
Liberals are like libertarians in this regard. Housecats that don't understand what the actual source of stability and prosperity is.