NPR misrepresented the nature of the crisis in a comment introducing a Morning Edition segment on the pending default of Jefferson County, Alabama. It referred to the country suffering a debt crisis. This is not accurate.
The problem is one of Congress refusing to raise the debt ceiling. This would be comparable to someone losing their checkbook even if they had still had $20,000 in their account. They may face a problem getting money out of their account until they get more checks (or learn on-line banking), but there is no problem of a lack of a funds.
The United States will be in a comparable situation after August 2. No one thinks that it would have problems getting the money needed to pay its bills by borrowing in financial markets. The only problem is that Congress will have denied the government the legal authority to pay its bills.