Of course there were many tribes. The first Europeans to come here did not encounter closed borders. They encountered open borders. I don't know what is so hard to understand.
You brought up the convention on the 14th Amendment and with it "birth on American soil." So, that's where the birthright discussion began. You said it was a "rhetorical question," thus essentially a statement. I brought up jus soli because you made the aforementioned "statement."
"I was one before I became an American." One what?
A footnote may not constitute law, but if it is codified, say in 8 USC § 1401, then it sure is. You do know how they make laws out of court decisions, don't you?