I know the story of why Astor Johnson was born in Norway. The family was settled in Brooklyn. Marie, Nils' wife, left for Norway to escort her newly widowed mother Andrea Andersdr Engebrigtsen, to Brooklyn. She discovered she was pregnant after sailing, and so stayed in Norway to have the baby and wait until he was old enough to travel. Then they sailed back to the US, where her mother lived out the rest of her days in Brooklyn as well. There used be a portrait of Andrea in the house when I was growing up, which sadly no longer exists.
As for the 1880 census, I read that fire destroyed part of it, but I have no proof. I've never been able to find any part of it that contained any of my family history. A pity, whatever the cause.
Thanks for your interest.