It sounds like what you want to do is narrow in on one predecessor to today's immigration policy. Probably the most frequently mentioned precursor (in my brief skimming of the literature) is the Immigration Reform and Control Act of 1986. You can see a summary of the bill and its complete legislative history on Thomas, the legislative section of the Library of Congress.

The original cosponsors of that bill wrote an op-ed piece that appeared in the Washington Post last fall, which might be helpful in thinking about ideology and intent.

Justice Talking, an NPR program, did a program on immigration reform last year, which I seem to recall included some discussion of the history of immigration policy in the US, thought that's not apparent from the web summary.

NPR and the New York Times both have excellent collections on immigration, and both include some history and background that might be helpful. A lot of the Times stuff may be hidden behind a pay wall, but if you get an article citation, you may be able to find it through a library database. If you're at a college or university, you probably have access to Lexis Nexis Academic through your library, which includes the NYT. For more background, CQ Researcher is another good source, if you have access to it.