Under that same theory Donald Trump is a British citizen.
Actually, he likely is a British national. Yep, trump likely has dual nationality. Although his mother became an American citizen before he was born, according to British law, she never properly renounced her British citizenship. British nationality passes from the parent to the child (so long as the parrnt, at some time in his/her life, lived in Great Britain.
Has trump renounced his British nationality? Does that raise questions of loyalty? More importantly, does that mean he’s not a natural born citizen? Of course not. The laws of another country granting citizenship or nationality are irrelevant to our law.