On Thursday President Biden officially established Juneteenth as a federal holiday, an achievement born of rare unanimous support in the Senate and an overwhelming majority of votes in favor in the House of Representatives.  Juneteenth is already recognized in 47 states and celebrated in communities nationwide, and was examined on episodes named after the holiday on “Atlanta” and “Black-ish.” Each is extraordinary. But to truly understand why the initialy response to the bill passing the Senate was mixed, to put it mildly, it’s best to revisit the “Atlanta” take on “Juneteenth,” which stands among the series’ best. The show’s interpretation of how this holiday may translate to the masses turns out to be more accurate, psychologically speaking. That it premiered in 2016 matters little, because the surreal mental and spiritual contortions shaping the episode’s comedy are inspired by the same political and social reality in which we currently exist. Biden called this year’s observance “the first that our nation will celebrate all together, as one nation,” a hopeful assessment given the circumstances. Getting Juneteenth to be a federally recognized day of observance …