The current law enumerates non-citizens, with Supreme Court decisions to support that practice. I don't know if the law requires counting of illegal immigrants, infiltrating Nazi saboteurs, and touring Italian tenors, but in practice, they are counting everyone including Cartel drug mules if they can.
In the 1860 census, my great-grandfather (9 years old) was listed twice--once with his parents and once with another family (I don't know why he was staying with the other people--don't know if they were relatives of some kind). Potentially that could have given Virginia an extra seat in the House of Representatives, but since Virginia was out of the Union from 1861 to 1870, it didn't make any practical difference.
“I don’t know if the law requires counting of illegal immigrants, infiltrating Nazi saboteurs, and touring Italian tenors...”
I am actually in favor of the touring Italian tenors.
Good one.