Perhaps there IS a problem with using the 14th Amendment.

[HopeHoops]

It is the use of the phrase "incurred in aid of insurrection or rebellion against the United States" in Section 4. Since the majority of the debt was incurred under GOP presidents, clearly agents of anti-United States activities, individuals, and organizations, those debts aren't covered by the 14th Amendment. In fact, the 14th Amendment states that such debts "shall be held illegal and void", an exclusion originally inserted to prevent the US government from taking on debt incurred by the Confederate states. Perhaps this is why Obama has resisted invoking the 14th.