You're talking about the 2nd Amendment right? The 14th Amendment is clear, regardless of the intent when it was written.
Apparently, not as clear as you think. First, the 14th Amendment is long and more complex, with 5 sections addressing separate topics related to citizens' rights and representation. Section 1 is the topic of discussion here.
The first sentence says "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."
If being born here (or born to US citizen parents) were the only requirement, it would read "All persons born or naturalized in the United States are citizens of the United States and of the State wherein they reside."
The tricky part of the actual passage is the presence of the clause "subject to the jurisdiction thereof." The word "and" simply means that this is an equal requirement to "born or naturalized in the United States."
The meaning of this phrase was the subject of the Supreme Court hearing the case US vs. Wong Kim Ark. In that case, Wong Kim Ark was determined to be a US citizen with all the rights and responsibilities thereof. The difference in that case and the current situation is that Wong Kim Ark's parents were citizens of China, in the US legally under agreement between the two nations.
The law, on the basis of the 14th Amendment language, has always differentiated citizenship based on why the parents are in the US. Children of diplomats don't get US citizenship. If we were invaded/occupied by a foreign country, their children would not get US citizenship.
What Trump hopes to put before the Supreme Court is the current situation, which is farther from the intent of the 14th Amendment and the decision in US v. Wong. Can the children of people here illegally be deemed US citizens? Does the crime prevent the benefit of citizenship ("but-for" causation) as it does in other areas of law?