Ok, I have a question for you.
How could the Fourteenth Amendment bestow citizenship rights on American-born former slaves or children of former slaves, if their parents were not citizens? Certainly the Emancipation Proclamation didn't do it, or there would have been no need for the Fourteenth Amendment. According to your interpretation, they were not "subject to the jurisdiction" of the United States because they inherited the foreign citizenship of their parents. If that is not the case, by what mechanism did slaves lose their citizenship of their country of birth? Kidnapping? By your logic, if former foreign-born slaves did not become American citizens by actively seeking naturalization, then their children, and their children's children, and their children's children's children, ad infinitum, would not be citizens today -- and the Fourteenth Amendment would be meaningless. And if you argue intent, why didn't the framers just write the Fourteenth Amendment to cover the descendants of slaves, and slaves only?
It's an Amendment to the Constitution. That was its intent. It was ratified. Nothing more need be said. Sheesh.
They may not have been citizens prior to the amendment, but they were undoubtedly subjects. They owed absolutely no allegiance to any foreign nation. Only the U.S.