That is why it won't happen. It would be too disruptive. I think they would make some "Defacto Officer doctrine" to let the past aliens alone, and thereafter allow the executive branch to prohibit future birthright citizenship.
Once President Trump pulls the birth right citizenship wild card out from under his sleeve, we may be fairly amazed at what can get done and how quickly it can happen
Birth right citizenship for the anchor baby children of illegal aliens is absolutely unconstitutional and everyone knows it
If the feckless losers in Congress force President Trump to go all the way to the Supreme Court for a formal interpretation of the 14th Amendment, all hell going to break loose