The problem with our economy is the trickle-down policy instituted decades ago by Republicans -- a policy which says the rich and the corporations don't need to pay their fair share in taxes (and that they will share this money saved from not paying taxes with the rest of America). The whole idea was ludicrous, and anyone with common sense should have know it would fail -- and that's exactly what happened.
We now have a situation in which many corporations don't pay any taxes at all -- thanks to tax breaks, subsidies, and the ability to hide profits in off-shore accounts. It has gotten so ridiculous that many giant corporations even get tax breaks for exporting good American jobs to other countries (where they can more easily exploit the poor with indecent and unlivable wages). And the rich, who benefit the most from this country, are paying a smaller percentage of their income in taxes than many in the middle class -- thanks to tax deductions and being able to declare much of their income as a capital gain (which means they get to pay a smaller tax rate than if it was considered earned income).
Through their tax advantages for the rich and the corporations, the Republicans have been able to dismantle much of our progressive tax system. While the working and middle classes must pay a tax rate that increases with their income, the rich and the corporations no longer do that. Note that we now have a system where corporations like General Electric pay no taxes at all even though they had billions in profits -- and a rich man like Romney, who made more than $20 million, could get away with paying a 13% tax rate.
The problem with the American economy is that the government doesn't have enough revenue -- and that is not because the spending outstripped the revenue, but because the revenue was cut drastically for the rich and the corporations. If the rich and corporations were just paying the same rate they were paying 30 years ago, before the Republicans initiated the "trickle-down" economic policy, the economy would be in much better shape.
But the Republicans stubbornly refuse to allow that. Through their control of the House of Representatives and their abuse of the filibuster in the Senate, they have blocked every attempt to return to tax fairness. It is just one more reason (among many) why they must be voted out of office as soon as possible.