The value of the dollar decreases by a lot, meaning our economy is essentially shot. More than that, in order to keep the country running, the government borrows money. They do this by selling off government bonds to organizations and companies, essentially an IOU. Even more than that, the US dollar is more or less the world currency, a lot of business is done with USD. In other words, for every US dollar the government spends, they owe 19 cents of it to someone else, which is where debt accrues. I'm paraphrasing a lot here, but that's the basic gist of it. So if they default, that means they can't pay off debts, and the value of the US dollar decreases making it an undesirable currency for world trade. It also means we don't have a lot of money to run the country off. Basically our economy wouldn't be in a very good state. It also would not be local to just the United States, we would take down a few other people if we were to default, it's kind of comparable to the beginning of the recession, it didn't just effect the United States, it had a terrible effect on countries around the world. That's the gist of it, if I'm wrong I'm sure someone will correct me. I don't want to say it's the end of the world, but we would all be in a very rough spot if it were to happen. I have hard time straying from the thought that we should just let it happen. The world powers have been toying with our livelihoods to make a point for so long, let them burn in their own mistakes. It would be at the cost of a lot of people, but I don't see there being an end to the cycle without them screwing up everything and paying for their incompetence. I do want to say that both parties have been doing this ever since the debt ceiling was a thing, obviously this case is a bit more severe considering we're so close to the deadline, but I also don't want to use fear to make a point like so many people do. The situation we're in isn't new necessarily, but the circumstances are a bit different.