you’re joking, right?
if william & kate’s kid were born in NYC, they’re US citizens (check state.gov for info on citizenship at birth rules)
if you’re talking about TCruz, anyone born in canada is a canadian citizen at birth. the fact that TCruz had an American mother was secondary and led to his US citizenship
it also gives him the ability to choose which citizenship he wants to use... which negates the possibility of him being a natural born citizen of either
they’re == he’s a