Republican presidential contender Patrick J. Buchanan chided President Clinton and the GOP-controlled Congress yesterday for failing to secure U.S. borders and endorsed legislation that would deny automatic citizenship to children of illegal immigrants. Buchanan also called for legislation making English the country's official language and for at least a doubling of the Border Patrol. And he called anew for two other components of his immigration policy: a double security fence along the most porous section of the U.S-Mexico border and a five-year moratorium on virtually all immigration so that newcomers to the United States could be assimilated.