Excellent analysis.
Another way to look at is is that if Trump would have started off by saying "Congress should look at birthright citizenship", the statement likely would have gotten swept under the rug and ignored. But using his typical hyperbole baited the press to bringing the issue to the fore, so how he's shifting the argument. But he's made it a part of the discussion where it wasn't before.
Like it or not, it can be an effective approach when the media is predisposed to only report what they think advances the agenda they prefer.
It's made a lot of us revisit the issue and think about it. I for one pulled the authorities, studied them and concluded that, yeah, birthright citizenship can indeed be limited without the impossible task of amending the Constitution. Sure, Trump has backtracked, but he's put the issue on the front page of every paper, and tossed it back to Congress to DO ITS MOTHERFLIPPIN' JOB.
And we all know, six days before the election, that the only way Congress would consider doing its job is if Republicans are elected.
Your take,
@Maj. Bill Martin , is spot on.