I'd like to see a citation for that claim that immigration was more permanent back in the 19th century. There's always been a portion of those who came here intending to work for a while and then head home, some of whom later decided to stay. I can believe that the fraction who did so has changed over the decades, but I'm doubtful it's been a big change.
Return rates were very low for groups like Irish Famine Refugees and Russian Jews, who either had nothing to go back to couldn't go back due to religious persecution. They were much higher for Greeks and Italians, who usually came for work and often crossed the Atlantic multiple times.
