John Collins was certainly from Belfast and AFAIK lived most of his life there till his untimely death in 1941. He had 2 sons and a daughter and one of the sons - I think it was Benjamin Collins (but might have been Hugh) had an interest in his father's Titanic experience. The daughter Mary became Mary McKee after marriage and in the early and mid 1990s was living in England. At that time I was doing some research into John Collins and spoke to Mary McKee several times over the phone. She knew very little about her father because she was very young when he died but learned a bit from her brother Benjamin which I managed to make a gist of after several conversations.
One of the sons - I am almost certain it was Benjamin Collins - was living somewhere in the US when I was in touch with Mary McKee as above. She did send me his contact details by regular mail (I had no internet at the time, over 25 years ago) but we moved house ourselves soon afterwards and I misplaced it somewhere. Also, I lost contact with Mary McKee soon afterwards but I learned recently that she moved to Spain where she passed away in 2011. According to John Collins' bio on ET, she was his last surviving child at the time and so Benjamin and Hugh must have died earlier.
Was there a Benjamin or Hugh Collins among your American grand-relatives ie grandfather or grand-uncle? If so, might be worth checking if there is a connection.