A study done a few years ago revealed that the average American believe that NASA's annual budget is around 20% of the total U.S. expenditure. That, of course, is ridiculous. NASA's 2011 budget was somewhere around 0.6%, a number that went even further down in recent years. To illustrate how small that amount really is, compare put it next to the military, which was over 900 billion (with a B!) dollars in in the same year! In fact, if you put together every penny the U.S. government has ever spent on NASA over the agency's little over 50 years of operation (which includes all the satellites, the Hubble Space telescope, the mars probes, the Apollo program, and every mission that gave pride to millions of Americans) it would still add up to less than what the U.S. spends on its military in a single year! Another interesting tidbit: the American government had spent more on the 2008 bank bailout than on NASA's in the last 50 years! So next time, when someone tells you that the United States spends too much money on NASA, you will know better. The chart below puts the points discussed in a nice, visual form (special thanks to Steve Heroz for allowing me to re-post his image here).
Lastly, here is a short video from Neil deGrasse Tyson where he addresses the issue in a way I could never dream of (special thanks to youtuber, Evan Schurr, who edited it). Watch it, listen to it, share it!