Can someone explain to me what will happen when America defaults on it's debts and/or other calamity happens?

Leaving behind the left -vs- right thing, the network "news" talking points, etc... Can someone explain to me in an objective perspective what is going to happen when America keeps kicking the can down the road as far as repeatedly raising the debt ceiling? Will America definitely be defaulting on it's debts in the near future? If not, what else will happen? Also, I am wondering what a debt default will mean for the average American...is this where another Great Depression sets in, or will this be different?