The debt ceiling is one of the biggest problems in the U.S. It seems that government officials of the past and present seem to think they have some internal credit card that has no ceiling to it. The debt of this country is flat out ridiculous. I hate to say the the country needs a salary cap to work under, but we do.
The national debt is a real problem, while the fiscal cliff is an artificially manufactured crisis designed to make our Congress deal with revenue and spending in such a way as to balance our budget so the debt does not go higher. I don't see the fiscal cliff as unsolvable because it is the result of Congress being unable to agree on some measure to increase revenue and decrease spending. An awful lot of their disagreements seem to hinge on personal fears of losing the "fight' and at the current time we see politicians bungling around trying to save face over certain issues. When the consequences of their inaction become unreasonable, they will act.
From what I've read, the debt ceiling does not do what many people seem to think that it does. It is not a magical threshold that, upon being reached, freezes America's spending. All it is able to do after it is reached is restrain the Treasury from paying for expenditures that it has already taken on. Basically, it makes it where we can't pay back the money that we've ALREADY borrowed, but it does not restrict any future spending or borrowing. It seems to be an all risk and no reward situation. Per Wikipedia, "A January 2013 poll of a panel of highly regarded economists found that 84% agreed or a strongly agreed that, since Congress already approves spending and taxation, 'a separate debt ceiling that has to be increased periodically creates unneeded uncertainty and can potentially lead to worse fiscal outcomes.'" As for the fiscal cliff, sure, that could end up being terrible for the economy, but Congress will either reach a tiny compromise and move on or just continue to postpone the cliff's steep cuts and tax hikes.
The debt ceiling causes a lot of long term problems but they're largely poorly defined, the fiscal cliff we can look at and directly equate it to what's going to wrong. No matter who you are, if we go over this, your taxes will go up. Period. That threatens the economy, it threatens it right now, and we can point at why.
The debt ceiling is not even there anymore. It has been risen countless times and the bigger concern now is that, the debt building itself is getting taller, and taller, and soon it will fall. The debt ceiling does correlate intimately with the fiscal cliff because if the US does not throttle back on spending money it does not have, it will rubber band back hard.