I doubt we'll default on our debt. No need too. Just print money to pay it....they call it "monetizing the debt"....you just inflate it away.
There's no good way out. You can monetize it, or pay it, or default. Paying it would require the Mother of All Austerities for a very long time. More politically palatable to monetize it. Default would cause a severe contraction but it'd be over sooner than any other sceanrio. But that would make the Great Depression look like good times. I think a lot of people would starve.
Just compare it to your household budget. If you spend more than you make you have to borrow the shortfall, and eventually the payment on the debt will consume all your income. Of course if you can go down into the basement and print all the money you need...no problem. But you can't. Only the Government can do that.
In that scenario cash would lose its value rapidly. Keeping cash right now isn't too painful, but it still has a negative real return. What pitiful return you get is still more than eaten up by taxes and inflation.
There is no risk-free investment. Not even cash, which is actually a guaranteed loser. Granted at the moment it is a small loss but anybody who remembers the inflation of the 70's knows what I'm talking about. Inflation was in the middle teens, maybe more, and Government Bonds paying 10% were called "Certificates of Confiscation". Of course that was the bottom and the perfect time to buy.
Where do you think we are now? In spite of stimulus that dwarfs anything in economic history we have paltry economic growth given that we've thrown everything we've got at it. The dollar of growth we get per dollar of stimulus has been falling ever since they started stimulus decades ago. What happens if stimulus fails to generate any growth? Game over.
Of course the $64,000 question is what do you do about it on a personal level.