Hello I am looking to apply for an LLM in Transnational Law or International and Comparative law. Can someone tell me where I can find the school rankings specific to these fields for U.S. schools?

Hi! You can find the most elaborate academic rankings from Brian Leiter's Law Schools Rankings. As regards international and comparative law, you can find his ranking here: http://www.leiterrankings.com/faculty/2003faculty_international.shtml

My own ranking (not a "scientific" one, to be sure) is that NYU is the best place to study public international law while Yale is the leader in comparative law.