The "underground" of the title refers not to crime but to the half-hidden world of two-bit hustlers, "artistic" poseurs, aberrant lifestyles and shattered dreams. Small-time Manhattan opportunist Eric Mitchell latches onto Patti Astor, a once-popular movie star fallen into penury. He briefly lifts her spirits, but in the final analysis betrays her. Astor sorrowfully decides that she'd rather not live any longer. Lensed in 16 millimeter by producer/ director/ star Eric Mitchell, Underground USA is occasionally effective, though for much of the proceedings it suffers from trying too hard to be the Big Apple counterpart to Godard's Breathless.
~ Hal Erickson, All Movie Guide