Mary was a McDonald, as her son Thomas Ross Cameron's death certificate states that as well as other references such as his obituary stating that his mother a Mary McDonald of keppoch.
The USA reference comes from a book titled An Extraordianry Australian by Father Paul Gardener. It has reference to Thomas Ross Cameron's parents Samuel and Mary and their connection with mother Mary of the cross MacKillop. Mary mackillops mother was flora McDonald.
I believe the Mary and Samuel you have found is a different family but fit the time frame.
Thomas Ross had siblings as follows
Mary Hannah Angus and Alexander
