All persons born or naturalized in
  the United States, and subject to
  the jurisdiction thereof, are
  citizens of the United States and
  of the State wherein they reside.

The SCOTUS long ago held that "and subject to the jurisdiction thereof" does mean something. For example it means that children of diplomats and tourists are not U.S. citizens because those diplomats and tourists are not "subject to the jurisdiction thereof". There were debates in the Congress at the time about this.

Whether that applies to other cases is yet to be seen. But let's not pretend like it's obviously clear that the 14A means birthright citizenship no matter the circumstances, or that there aren't controversies here for the courts to settle.