Oh come on, soverign debt is about as far from being "a market" as possible....

I'll believe the yields mean something when the US Treasury issues a special series of bonds that are forbidden to be owned by the Fed or any entity with access to the discount window.

The benefit of a large, well-equipped military is that you get to tell people whether or not you're/they're going to pay your/their debts. For as long as your population is willing to pay for its prosperity in blood.

There's a lot of countries with lower nominal yields that are not known for their military prowess ... like Greece. Yes, greek bonds have negative yields.

Greece has the miliary power of the entire fucking European Union (and its allies) behind them, for as long as they're willing to suffer for the benefit of France and Germany.