The US should never default on any debt it has incurred. The arguments over the debt ceiling are ridiculous and demonstrate a lack of basic knowledge. The increasing of the debt ceiling does not add to the deficit, it is to permit payment of debt already incurred, meaning we already spent the money and have an obligation to repay. The government is no different than anyone individual who buys using credit, you agreed to repay. A renegotiation of the payment plan is certainly permissible if both/all parties to the transaction agree.