Complex sentence: Only Canada is not a CSA "client state", becoming home to refugee abolitionists and escaped black slaves; the American wall constructed to separate the two countries is called the "Cotton Curtain" (counterpart to the real Iron Curtain).
Split into simpler sentences: Only Canada is not a CSA "client state", becoming home to refugee abolitionists and escaped black slaves. The Confederates construct a wall along the border between the two countries called the "Cotton Curtain" (counterpart to the real Iron Curtain).