Since this post is the first google result for sugar protectionism, I’ll post a collection of better resources:

Mark Groombridge, “America’s Bittersweet Sugar Policy,” December 2001, PDF
Kim Elliott, “Big Sugar and the Political Economy of US Agricultural Policy,” April 2005, PDF
Jose Alvarez and Leo C. Polopolus, “The History of U.S. Sugar Protection,” June 2002, HTML
Omer Gokcekus, Justin Knowles and Edward Tower, “Sweetening the Pot: How American Sugar Buys Protection,” 2003, PDF

Please submit more links in the comments.