The total population of registered hunters in America today ranges from 23 million to 43.7 million individuals. (Based on annual data provided by the U.S. Fish and Wildlife Service.)
I thought that number sounded inflated, so I checked. USF&WS data I found states that 12.5 million Americans, age 16 and older, hunted in 2006. If you add in youngsters not required to have a license, the total is probably somewhere in the neighborhood of 15 million. That figure has been fairly constant for a few years now. Good that those numbers are not declining, but bad that we're not adding to them.