What you say makes sense: Cancel all of the debt simultaneously and start over. The implementation is another matter entirely. While I appreciate we shared common sentiment, neither of us have a magic wand.
Importantly, there is a historical precedent. The Panic of 1837.
When the Erie Canal was built, based on a State bond issue, it was a huge success, coming in on time and budget, making a lot of people lots of money. So a handful of other States tried to do the same thing, issuing bonds to make their own, impractical canal systems.
Most of these bonds were paid for with private bank issued currency. After a huge number of bonds had been issued, the whole scheme started to fall apart. Then President Jackson, just before leaving office, issued a decree that all private bank money had to be backed by gold. This wiped out hundreds of banks overnight.
And since the projects were unworkable, the States defaulted on their bonds, resulting in the worst depression the US experienced up until the Great Depression.
The practical result was that these States had no credit for about 30 years, so had to maintain balanced budgets and not engage in speculation of any kind. Only later were they able to rebuild their credit. The bondholders never saw a penny of their investment.
So how can the USG get out of its debts and obligations? Other nations have defaulted on their debts as well, and in recent years. But these countries were obligated to rebuild their credit, so had to abide by the demands of the IMF. The US does not to any great extent need the rest of the world.
But this would entail leaving many international financial organizations, such as the IMF, the World Bank, and many other treaties. Mostly just administrative changes.
As far as Social Security, Medicare and Medicaid, the government would pass a balanced budget amendment and possible a line item veto, then just announce that the constitution no longer permitted them to pay SS or medical costs.