When did the United States Of America, default On their debt, and become a private corporation

The United States has never defaulted on its debt in a way that would classify it as becoming a private corporation. There have been instances in U.S. history where the government faced financial challenges, such as during the Civil War and the Great Depression, but these did not result in a formal default that would lead to a change in the status of the U.S. government. The idea that the U.S. has become a private corporation is a conspiracy theory without basis in fact. The U.S. government remains a sovereign entity. It operates under a constitutional framework and is funded primarily through taxation and borrowing from both domestic and international lenders. If you have specific events or periods in mind, please clarify, and I can provide more information.