What will happen to the American economy if the debt ceiling isn't raised and we end up defaulting? BELOW!!!!?

There seems to be fears that we're going to end up worse than Greece is now, and collapse economically from not raising the debt ceiling, which will make us run out oif money, China will let us go, and we'll die out. IS this all true??? Are we headed for an economic collapse by debt defualt that will bankrupt us, and turn us in to Zimbawe???