"... most americans will realize that the only way to continue the properity and global power we've enjoyed over the past century is to import more people ..."

Given the global externalities produced by that prosperity and global power, why is it obvious that "most americans" would want that to continue ?

It may, in fact, be the case that importing citizens is the only way to continue this, but it's not obvious that there aren't other modes of living and growing.

Living things are born, they mature, then grow old and die ... mature living things don't consume the same resources or create the same outputs as juvenile living things. That's not necessarily bad ...