Steve James’ latest masterpiece—and despite his creative modesty, the man has many, from “Hoop Dreams” to “The Interrupters” and other interrogations of America and what we expect from her—takes a massive subject and breaks it down into fractal pieces. Those discrete bits, made up not so much from Subjects and Themes but from the people who his camera frames in a quiet kind of curiosity, are then assembled together into “City So Real,” an expansive five-part portrait of Chicago tussling with its purpose, identity, and future in the new millennium. It’s a noble, heartfelt, and eye-opening look at the American city, matching the scope of Frederick Wiseman’s recent scoping of a similarly fractious Boston in “City Hall,” but giving it more of a warmly human pulse.