Waste, fraud, abuse, and earmarks need to be reined in, but without addressing the big three - defense, SS, and medicare, all else is whizzing in the breeze. All three have large, unyielding constituencies, though.
I doubt the "banks" will close their windows on the Fed Gov, but bond rates will likely go much higher eventually, which will make the other "biggie", interest on the debt, all the more intractable.
Defense is relatively easy to fix, as is SS, assuming the willpower to do it. Medicare will have to survive the baby boomers getting older and sicker, is ill prepared to do so, and no solution that isn't painful and costly exists, at least that I'm aware of.
The primary problem is the citizens who believe the politicians when they say taxes can be low and services high, no worries...