Every month when we got paid, the government gets our money in the form of withhold.
OK. Just assume US gets all the money on Jan. 1 for the sake of argument. Since US must pay interest by law, it can, and should set that 1/9 of the money on Jan. 1 to pay the interest for the whole year regardless of the new debt and should never default.
Default is a choice of not setting priorities. It has nothing to do with debt ceiling.