At the turn of the millennium, a five-year-old boy from Cuba found off the Florida coast on Thanksgiving became the most talked about child in America. Elián González had left Cuba with his mom and a dozen other migrants, trying to make it to the U.S. but on the way, the boat capsized. Elián’s mother drowned. Before she did, she tied her child to an inner tube, saving his life. Relatives in Miami — Cuban exiles — took the boy in. His father in Cuba wanted him back. The ensuing international custody battle over Elián González became its own mini Cold War, pitting Cuban exiles in...