The Supreme Court has never once in American history issued a ruling on birthright citizenship.
Let's see what the Supreme Court actually rules on this issue. It's long past due.
Well you are right that the SC has never ruled on birthright citizenship but there is a case that already went to the SC
SC decision in United States v. Wong Kim Ark in 1898 when it ruled 6–2 that "14th Amendment affirms the ancient and fundamental rule of citizenship by birth within the territory ... including all children here born of resident aliens."
What would get contested if Trump wanted to go down this route is whether the President can make a change to the amendment with an Executive Order. I am all for having the amendment clarified so its not ambiious but I will be damned if I want any President to make any changes using an Executive Order.