New York's Museum of Modern Art cannot but feel pangs of regret as it parts with one of the most significant art works of the 20th century. But a home in Spain for Picasso's "Guernica" is fitting and proper. Henceforth the masterpiece will hang in the Prado Museum not only as an enduring reminder of the horror of war but as a stirring symbol of the end of Francoism and the restoration of democratic liberty in Spain -- the conditions under which the artist stipulated it should be released to his native country. The United States has not lost "Guernica." It has helped to broaden its message.