If the debt ceiling is not raised, then the Treasury prioritizes the items to pay with its ongoing revenue stream and it could choose to pay interest on the debt so the U.S. does not default on the sovereign debt.
Then the Treasury prioritizes the items to pay with its ongoing revenue stream. The debt ceiling is not raised. It could choose to pay interest on the debt so the U.S. does not default on the sovereign debt. The debt ceiling is not raised.