While Greta Gerwig’s “Barbie” live-action remake captivates audiences through its shiny and perfectly pink trailer, “Saturday Night Live” is putting a spotlight on the less glamorous, overburdened world of the American Girl Doll — disease, death, unpleasant history and all.“People can’t stop talking about the trailer for the new ‘Barbie’ movie, but not all dolls live in a dream house,” the narrator says in the sketch’s opening. “Some are bigger, younger, sadder; some dolls are American Girls.”As the trailer for the historically accurate flick introduces its struggling heroines, each sob story is worse than the other, from Samantha (Chloe Fineman) watching her parents die on a boat to Molly’s (Molly Kearney) father’s being a prisoner of war.