Song meaning

When asked if they really believe that Edward Teller was the biggest killer in American history, BR answered: "Edward Teller is named in the song 'The Biggest Killer in American History' because he is a part of the web of people and institutions that are collectively known as the military-industrial complex. It is this complex that is criticized in the song, not the individual scientist himself. We respect his monumental scientific achievements, and acknowledge that the times were stenuous for scientists during the second world war. But his desire to build larger and more deadly bombs after the war cannot be ignored. In life one must be rewarded for his/her achievements, but also held responsible and criticized for malicious intent. And we don't believe that you achieve peace through war."

A fan asked Greg Graffin at a concert who the biggest killer in American history was. He replied quite matter-of-factly that it was the US military.
Hetson on the other hand said it is Edward Teller (mentioned in the song).

More about Edward Teller.