The populations of the United States and of the world are not sustainable. Even with current technologies, the ecological side-effects of overpopulation are destroying the earth. As petroleum production declines our farms will become unable to feed the current (and still growing population).
In addition to moving to a rational immigration policy, we must have a public policy on sustainability, the size of our population, and therefore on reproduction (the number of children each couple can have).
I believe we can start heading in the right direction almost immediately without using coercive methods. We need to educate our citizens to realize that, until our population has reached sustainable numbers, to children must be the maximum per couple. To provide incentives we need to end the income tax incentives that exist for having more than 2 children.
One concern already expressed by citizens is that both misguided individuals and religious cults may encourage their members to cheat on the 2-child guideline. I think we should wait and see whether that happens. If it does then I believe we can devise measures that will discourage cheating without infringing on human rights. In particular I think we need to let those who quote "go forth and multiply and fill the earth" know that the earth is filled. It is time for them to start heading some more important moral precepts.
It is crucial that methods of planning reproduction be legal and readily available to every fertile person.
A number of non-profit organizations can provide additional information on population planning: