Inflation, growth and defaults.
Trump has already de facto seized, and the Republicans in the Congress ceded, the power of the purse. Do you really think impounding interest payments is beyond the pale of possibility?
A balanced budget is a popular idea in theory, but very few people actually want to see it happen once they find out what their own cost will be. The politicians are going to do whatever it takes to mollify voters and keep their jobs.
When Democrats leave surplus or just lower speed at which debt goes up ... debt is still their fault.
I truly hope so, otherwise the only buyers for US Treasuries will be Social Security.
Defaulting on sovereign US debt would be something that would make me rapidly look for an exit from the United States.
It will happen in phases: 30 year bonds become 100 year bonds, foreign countries get payments, delayed, etc.