This news from Havana: In the United States, the images of Elián González being showered with Christmas toys are proof of generosity and plenty; in Cuba, those same images are offered as proof of his cynical exploitation and the crass materialism of Fidel Castro’s enemies in America. The six-year-old Cuban boy, found clinging to an inner tube off Florida last month after a harrowing voyage in which he lost his mother, has become Castro’s political poster child. Cuba’s aging leader has launched a campaign of well-attended rallies, televised appearances and advertisements that have rallied his countrymen and galvanized many younger Cubans throughout the country.