I also thought that someone would sooner or later have to pay for all that free money, but here it is being thrown in by the trillions like old paper that will be recycled and put back into use again.
No, the debt will never be paid, at least if we consider never as our lifetime.
They will roll on this debt till the world's ending as although it sounds ridiculous, this game can go on and on forever. The US debt is not like our debts, we can't print money and we can't move it from one balance to another and say we're ok since both are our pockets and they cancel each other.
Everyone that comes with promises to fix it realizes that it will take way too long to do so and at the same time that it will not blow up during the period he is in charge so he just throws the towel and continues as his predecessors, Trump came with the same promises, how it ended we all know it. Biden doesn't even care, his whole plan is more spending.
The state will issue more bonds the federal reserve will buy the debt and so on and on until the debt will simply be unplayable or unserviceable at which point probably they will push the reset button and ...there is no more debt. I think it happened with companies in your country also during the 1990-2000 period when entire debts were erased as the state owned companies were indebted to the state itself. That's the way we're heading here also but of course with more brutal consequences as the actors are a bit different.
I'm really interested in when (and whether) things will go downhill at one point without the possibility of stopping?
It's already going downhill, there is no way this trend can be reversed in at least a decade, but luckily for us (of for me at least as I don't have a clue what's your age) it will probably crash after the moment I don't care anymore.
