The first two pie charts are simply displaying "Revenue" versus "Expenses".... to be more representative the size of the two pies should of been in relation to each other, in which case the top pie would be far smaller than the bottom pie. What you should also be realizing is how unteneable our position is, and how there will be no easy answers to fix it either politically or in real terms trying to adjust to any standard of living that would account for any sustained ability to reduce the deficit.
The short term "easy" answer to cut spending is to let other countries begin to police themselves, and draw in our forces from the 150 (??!) countries they are stationed - but at this point I suppose "military" is a major US employer so that would cause a lot of lost jobs. If you tried to live your life with 40% of revenue from credit cards or other such borrowings you wouldn't last long, but this shows you in living color - that's "how we do it!". In the expense chart, if you project how this will look in 2020 v 2010 the "Medicare" and "Net Interest" portions should both be exploding higher to be the top 2 outlays.
If you are trying to teach your child how to balance a budget please don't show them these graphics. On the other hand - showing how not to do something is sometimes the best teaching tool.
Revenue

Expenses

The next two put revenue and expenses as % of GDP in perspective over time; the 2nd chart effectively "nets" the data from the 1st
Historical Total Revenues and Expenses as % of GDP

Historical Deficit or Surplus as % of GDP

[Jun 12, 2009: NYT - America's Sea of Red Ink was Years in the Making]