Already been over this, OF COURSE. Just because American citizens may get access doesn't mean every citizen of the world deserves access. Have Americans apply, and if they are found to actually be Americans, and not illegal aliens or actually living and working in Cuba, they might get access.
It simply doesn't make sense that we have to give every right we give Americans to everyone in the world. Do you want everyone in Africa on US welfare? Well in your case, probably.
That model might just work whenever the software is actually sensitive (and very little is). Why don't you write up a license? Of course we'd then be locking ourselves out from the contributions of talented foreigners, so we wouldn't be able to expect as much improvement as we'd get with real open source.