The 14th Amendment
"All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and the States wherein they reside."
Key phrase here "and subject to the jurisdiction thereof". A legal immigrant, even though not a citizen, is "subject to the jurisdiction" of the US.
An ILLEGAL alien, coming here in violation of US law, does not fall under the definition. See here and here.
“The 14th Amendment “
The 14th Amendment has nothing whatsoever to do with natural born citizenship. The 14th Amendment can only authorize naturalization at birth and naturalization after birth, the 14th Amendment to the Constitution , and the Civil Rights Act of 1866 are all legislative acts and forms of Positive Law. The Supreme Court of the United States case law voided the Civil Rights Act for being unconstitutional, because it violated key parts of the Constitution without a proper Amendment of the Constitution. That is when the 14th Amendment was enacted to make the Civil Rights Act of 1866 a Constitutional act. Likewise, the Constitution and the Congress lack the power and authority to legislate definitions for Natural Law that predates the United States and the Constitution back into the prehistoric ages of mankind. Natural born citizenship is a branch of Natural Law, which is beyond and outside the jurisdiction and powers of Positive Law.