Several Librarians contributed to this answer.
1.
You might try contacting the ALA Office for Intellectual Freedom (http://www.ala.org/ala/oif/intellectual.htm). I didn't catch anything by skimming through their web site quickly (and searching the ALA site is a pain, as you may have noticed), but they do keep track of challenges and might have some records (or at least ideas of where to look) that might be useful.
2.
In Library Literature, the search: multicultural* and attack* gets 2 hits; multicultur* and collection* gets 56 hits but may miss the mark on this one.
In ERIC, possible searches include: multicultur* and librar* and politic* (32 hits). Lexis Academic is a much trickier source on this one - the Legal Research / Law Reviews ? all aval dates search: ethnic! and (challenged books or challenged materials) gets 12 hits, possibly worth looking into a couple of them:
Copyright (c) 1983 Texas Law Review Texas Law Review, October, 1983, 62 Tex. L. Rev. 197, 48339 words, ARTICLE: The Search for Constitutional Limits on Governmental Authority to Inculcate Youth., Tyll van Geel*;
and POSSIBLY - Copyright (c) 1987 Michigan Law Review Michigan Law Review, November, 1987, 86 Mich. L. Rev. 266, 40013 words, ARTICLE: SYMBOLS, PERCEPTIONS, AND DOCTRINAL ILLUSIONS: ESTABLISHMENT NEUTRALITY AND THE "NO ENDORSEMENT" TEST., Steven D. Smith
Still in Lexis Academic/Legal Res/Law reviews / All years, the search: immigrant! and (challenged books or challenged materials) seems less promising; it gets 12 hits, but "challenged materials" seems to be mostly LEGAL materials, etc. in specific trials. Possibly a search in Lexis / Legal News would help; but figuring out a strategy is even dicier there: challenged books gets only 5 hits in ALL years, full text. Before trying Legal News, I would first try: challenged books in General News/Major Papers - 67 hits in "all dates"/"Headline, Lead Paragraph..."
Lexis involves a lot of plowing through text (and references if you look at Law Reviews), but the "KWIC" format will usually tell you if an article or review is worth looking through.