I think the reason why GP is currently at "-1 Troll" is that the first line of the post says that US Treasury bonds have junk status. When you lead with an easily verifiable, factually incorrect statement like that, nobody will take you seriously.
But since there is, apparently, a large crowd (including several senators) who believe that the rest of what he wrote is "the truth". I will try to respond.
Yes, it is true that the US, like most other countries, will never pay off its debt. The way fiat currency works is that inflation continously transfers wealth from those who save to those who borrow. This means that if you have the credibiliity to be able to borrow, then you should do so. The federal government has this credibility, and therefore it is more profitable for it to invest in things like infrastructure and education than to pay off debt. (Even feeding the poor can be seen as an investment, because they will likely generate tax revenue in the future.)
I personally dislike the idea of fiat currency. I think it is deeply unfair the way we transfer wealth from those who cannot borrow to those who can. But since those are the rules we play by, I do the best of the situation and borrow to invest. The US government would be stupid not to do the same thing.
The idea that the US could keep paying interest on its debt, without raising the debt cieling (popularly known as "prioritization") is simply false. Even if it were legal (which it is not) it wouldn't work. If the federal government stopped paying any of its bills, then the credibilty that allows it to borrow cheaply would be destroyed. At that point, you get the equvalent of a run on the bank. It would not be a matter of paying $300 billion per year in interest, but instead repaying the principal at a rate of $5 000 billion per year, which would cause bankrupcy in a matter of weeks even if all other payments are halted.