THX 1138 had its wide american release March 11, 1971. I noticed this review, dated March 12, 1971, mention the Buck Rogers opening which I found interesting. According to IMDB the original release had instead a one minute clip from "Things to Come" (1936). So either IMDB is wrong about this or the critic may have seen an earlier screening of the film where the Buck Rogers clip was included, thoughts?
The review show up in one of the documentaries included in the 2004 DVD.