The sentence that features an allusion is:
“Young people behind the Iron Curtain would see Selma and eventually tear down that wall.”
This sentence alludes to both the historical context of the Iron Curtain, which symbolizes the division between Eastern and Western Europe during the Cold War, and Selma, referring to the Selma to Montgomery marches in the American civil rights movement. The phrase "tear down that wall" also hints at the famous Berlin Wall and its eventual fall, which is a significant historical event related to freedom and change.