When I lived in Asia, this kind of thing was routinely handled by the inviting organization (Rotary in this case) posting a suitable bond that would be forfeit if their guest doesn't fly back home at the end of the visit. The inviting organization will then be very motivated to help their guest complete his travel as planned. The net cost to the inviting organization is small as long as the bond is satisfied. 

This greatly reduces people over-staying their visas in other countries. Don't see why it can't work in the US. Otherwise, our borders have to be sealed to anyone who might benefit from remaining in the US past their visa. Which is to say, most of the world.