I understand. I understood last time. If Americans believe their organs may go to illegal aliens, they simply will stop donating them.
Imagine how many more organs would be available if people could specify who can or cannot get them.
It would not really make that much difference because most people don't care much either way, they just don't make it clear they really want to donate or their families stop the process. Think also how unlikely it is for you to become an ideal donor. You have to be brain dead but have healthy ,still functioning organs. Then your family has to agree to donate, because they can hold up the works even if you register as a donor.
Actually, it's the recipient who can specify they won't take an organ from a white or black person, for example. They're stupid to do it, but can.
If you donate a kidney while you're still alive, you can direct where it goes.