The laws were different at the time. Actually, there weren’t very many of them. Besides, Churchill didn’t live in the US. He became of age and under UK law was considered a Ukian!
Yes, laws and their interpretations were very different then. At the time of Churchill’s birth citizenship by blood could only be passed on through the father. From what I have read of the early writings of our founding fathers, women were considered to obtain U.S. citizenship by simply marrying a U.S. citizen.