>Firstly, America as we know it has been changing dramatically and continuously since its inception. I don't see anyone mourning the loss of the Bourbon Democrats or tariff acts, but suffice to say they aren't here anymore.

It's been changing, sure, but the change you address is different from the change of say dropping a nuclear bomb on all our major cities or discovering sources of unlimited, zero-emission energy. The change I'm talking about, which is eliminating immigration law completely by making ANYONE able to come here is entirely different from the "continuos change since inception" that you're addressing.

By "what we have now" I mean the state of everything as it is today. The economy, the people, our values, our resources. When you increase the population and let ANYONE in, all of these things will change.

Whatever "what we have now" is, it is good, by assumption, because people are trying to get into it.

Therefore it's worth asking if that "whatever it is" will remain good in the face of any proposed changes.

If a nation faces some future peril due to some degree of overpopulation, while the world as a whole faces greater future peril due to a markedly larger degree of overpopulation, then the people of that nation are likely better off not opening their borders. I have yet to decide whether the present situation of the USA fits this description, but it is at least not far fetched.