Incorrect. The aiming point that was used by Kermit Beahan was the Mitsubishi Steel and Arms Works not the Urakami Cathedral.
Christianity was instantly wiped out of Japan with one fell swoop.
Incorrect again. There were ~15,000 Catholics living in Nagasaki. ~10,000 were killed in the bombing.
St. Mary's Cathedral was one of the landmarks that the Bock's Car bombardier had been briefed on, and, looking through his bomb site over Nagasaki that day, he identified the cathedral, ordered the drop, and, at 11:02 am, Nagasaki Christianity was carbonized, then vaporized, in a scorching, radioactive fireball. And so the persecuted, vibrant, faithful center of Japanese Christianity became ground zero, and what Japanese Imperialism couldn't do in 200 years of persecution, American Christians did in 9 seconds; the entire worshipping community of Nagasaki was wiped out.