Modern Monetary Theory is this big idea... and if it's right the US national debt is meaningless and we should suspend actual debt servicing. If it's wrong we're absolutely fucked.
Right now America is generally operating under the fiction that MMT is "actually like totally true guys" but we refuse to use QE to reduce the debt because, actually, we know it's fucking bullshit.
Does it matter that we owe 50 billion vs. 50 trillion dollars - not purely from the number - it matters that we're constantly transferring a huge chunk of our national revenue to debt holders. If we bit the bullet and QE'd that debt into oblivion that'd be fine, but everyone with an actual brain knows that's a terrible idea.