Aliens in the United States (number of aliens in the United States, by States, counties, and nationalities, who reported under the Immigration and nationality act during January 1965) Prepared for the Subcommittee on Immigration and Naturalization of the Committee on the Judiciary, United States Senate. (OCLC #184920)
I know now that the monthly catalog record for this title says “Aliens in United States” (missing a word), which is why my full title searches were not finding it. I continued my search using the SuDoc number instead.
I initially misread the second cutter in the SuDoc, first looking too quickly and seeing only an “A” with a flourish, and then recognizing it as “Ae”. That also turned out to be incorrect.
I had found the OCLC record already (no SuDoc number), so used the Find in a Library feature to check what other people had as its SuDoc number in their government document collections. I found a library with a slight different SuDoc number (another variant!):
before finally finding the correct one:
Y 4.J 89/2:AL 4/5
and spotting that those letters must start the cutter for ALiens.