There are those who will insist that anything coming out of the Heritage Foundation is biased and unreliable. And yes, there are issues to be taken with measuring spending and revenue in terms of percentage of GDP rather than in absolute or inflation-adjusted numbers. But the conclusions of this summary report (a deeper analysis can be found here) are so intuitively obvious that I'm willing to forego a thorough fisking of the analysis, or at least leave that sort of thing to an anti-Heritage partisan.
We aren't undertaxing ourselves into debt, we're overspending. Overall revenues did not fall all that dramatically with the Bush tax cuts of 2001; had those tax cuts never happened, we'd still be deficit-spending at dangerous and unsustainable levels right now. The real issue is that overall spending shot through the roof in the last year of the Bush Presidency and the profligacy only increased in magnitude with the shift of administrations from Bush to Obama.
You can argue that the spending is necessary. That Keynes was right. That taxes should be raised to make up for it so we can responsibly continue what we're doing. That to not spend the kind of money we're spending is inhumane, especially when economic times are tough. Or even, I suppose, that one day, the economy will grow so that our spending levels can be sustained. Some of those are more credible arguments than others; I decline to agree with any of them absent a showing that carried a heavily-laboring oar. We need to cut governmental spending. But what you'll have a hard time convincing me of is that tinkering with the tax rates is going to make much of a direct difference in terms of reducing the federal deficit.