Part of Wilco's identity at the time that A.M. was released was defined by the instrumentation they used, which led to their classification of "alt-country." They quickly outgrew this title—even by their second album, Being There—, but on A.M. it seemed to fit. This is because of the dry, organic studio treatment of the drums, the presence of both acoustic and clean electric guitars, the somewhat tuneless crackle and subtle twang of Tweedy's singing, and, of course, the presence of the banjo and fiddle on almost every song.
On "Passenger Side," a mandolin, played by Max Johnston, who also provides the fiddle part, replaces the banjo. Sandwiching the fat acoustic strumming, the mandolin serves as a plucky counterpart to the jangly electric guitar part, which, though not a twelve-string guitar, is still reminiscent of the folk-rock tendencies of groups like The Byrds. The fiddle part weaves in and out of the foreground, keeping the rhythm fluid and continuous despite the slow punch of the rhythm section. Ken Coomer plays the drums just behind the beat, so it sounds like the song is constantly trying to catch up with itself. In addition to creating a rootsy and organic musical texture, these techniques also work to complement the lyrics, creating a slow and late-to-react progression that somewhat recalls the movements of an inebriated person stumbling and swaying in the early hours of the morning after a night of heavy drinking.
The speaker is the most important part of “Passenger” because the song is about his demons and personal hang-ups, which reflect a more universal plight of the human condition. Everyone has certain experiences with dependency, whether it is dependence on a substance, a place, another human being, or something else entirely. The speaker's intoxication not only reflects his own way of neglecting his problems, but it also recalls our own tendencies to ignore the consequences of our actions, remain in the present rather than think about the future, and prolong our misfortunes in order to accommodate some temporary solution. Such a character can be found again and again in American literature, as in the case of Blanche Dubois, from A Streetcar Named Desire. Blanche Dubois similarly uses alcohol to escape her reality, or at least distance herself from it.
Perhaps it is easy to relate to the speaker of "Passenger Side" because his personality is not a mystery to us—he's not talking about some unknown or unique tragedy or predicament that few have experienced; all he talks about is being drunk and without a driver's license, unfortunately a very common predicament that symbolizes his being numbed to reality and unable to take control of his destiny. In addition to the literary connections, the speaker fits into the spectrum of musical tradition, recalling the aimless wanderings of country outlaws like Johnny Cash and Hank Williams as well as the punk disillusionment of groups like The Replacements, who were somewhat notorious for their alcohol abuse.
Tweedy's signature style of songwriting blends poetry with catchy hooks, melancholy with dry wit and a sense of humor. This is a trait that makes him one of the most respected songwriters in music, and while its origins can be found in the Tweedy-penned songs of Uncle Tupelo, it was in Wilco that these gifts really began to shine. "Passenger Side" is the perfect example of this amalgam, rendering an amusing scene and creating a well-defined character that the listener can relate to while also alluding to broader and more serious issues of dependency, alcoholism, and youthful uncertainty about the future. The structure of the song is somewhat standard for country and pop music, following a verse/chorus, verse/chorus, bridge/verse/chorus structure; but rather than a separate section entirely, the chorus is simply a repetition of the song's title with slight variation, more reminiscent of songs like Hank Williams' "I'm So Lonesome I Could Cry" or "Your Cheatin' Heart" than Johnny Cash's "Ring of Fire," or his story-within-a-song, "A Boy Named Sue."