American Indian sovereignty accounts for the difference.
sovereignty - ie subject to the jurisdiction
So why doesn't "French" sovereignty account for the difference? Why doesn't "Spanish" sovereignty account for the Difference? Why are "Indian" nations treated completely different from the offspring of all other nations?
There are only two explanations as to why someone would proffer your claim above. Intellectual Dishonesty, or astonishing ignorance. I routinely point out that the standard used for "Indian" Nations applied to NO OTHER NATIONS. Yet, people simply ignore this brutal refutation of their argument, and continue repeating it.
The unmitigated truth is that "birth on the soil" citizenship is NOT supportable by our history. One must do astonishing logical backflips to argue that it is, as demonstrated by your "Indian Sovereignty" argument above.