Like the crack in the bridge over the Mississippi, the actual time can't be predicted. But that crack (amongst the thousands of other bridge problems) was certainly expected, and no surprise when it finally happened. A country is no different from a house. If you don't keep up the maintenance, things will definitely break sooner or later. The US's infrastructure has been lacking maintenance for decades.

Many talk about the financial problems like the acrobat spinning lots of plates on sticks. He's having problems keeping them going, and those plates are getting wobblier and wobblier.

If I have to make a prediction, I'd say in the next 5 years or so. So don't take on too much debt for you to handle, and start prepping for very difficult times.