"Can you please let us know how long we have to stay before "we" can be called indigenous as well? 100 more years? 300? 500?"

Good question.  I know of lions, tigers and elephants born here, and yet everyone still considers them non-North American.  To suggest otherwise would invite laughter and ridicule since "everyone" knows that lions are from Africa etc.    I know Chinese, Tamils and Nigerians born here, and yet white folks still ask them where they come from, so as far as I can tell, if you are here after the next ice age, then you'd be Indigenous by that time.  But then again, maybe not.