Fourteenth Amendment
Section 1
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.
I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my ability, preserve, protect and defend the Constitution of the United States.
You just lie about the second part and have a government full of sycophants and a corrupt Supreme Court that declares that everything you do is by definition legal.
Look no further than the dissent to United States v. Wong Kim Ark (when the Supreme Court ruled that the passage you cited grants citizenship by birthright), written by Chief Justice Melville Fuller, the mastermind behind such legal opinions as:
Racial segregation is completely legal (Plessy v. Ferguson)
States can't regulate workplace conditions or enact maximum working hours laws (Lochner v. New York)
Income tax is unconstitutional (Pollock v. Farmers' Loan & Trust)
Anyway, he wrote:
the children of Chinese born in this country do not, ipso facto, become citizens of the United States unless the fourteenth amendment overrides both treaty and statute
and
[Birthright citizenship means] the children of foreigners, happening to be born to them while passing through the country, whether of royal parentage or not, or whether of the Mongolian, Malay or other race, were eligible to the presidency, while children of our citizens, born abroad, were not.
So in other words, he was willing to rule that the constitution is optional as long as you are using it against undesirable races in order to get his way.
Sophistry and bullshit, that's how. Authoritarians don't base anything on reason. It's all "because I said so, and because I have a gun pointed at your head."
It's why they used the language of "invaders". 14th amendment doesn't provide protection for invaders. This is the first step in working around the constitution.