But compared to other bonds, the US Treasuries are probably the safest. Even the Euro bonds are less safe. IMO. They are having big problems that will only get worse.
However if this all goes to hell, then you have an allocation to gold to cover the inflation fallout from the mess.
But in 2008 everyone thought inflation was coming when gas was $4 a gallon and climbing. But by the end of the year we had a deflation situation and Treasury bonds went up 30%. Nobody saw that one coming which is why portfolios should hold a wide variety of assets at all times and not try to use market timing.