This was a mistake. It was an understandable one, perhaps even a laudable one. But the ACC Tournament belongs in Brooklyn the way the Kentucky Derby belongs in Biloxi.

The league that invented the conference tournament is no longer the ACC housed mostly along Tobacco Road. South Carolina left decades ago. More recently, Maryland bolted for the Big Ten. The neo-ACC, as old-line ACC’ers love to note, includes more teams with a Big East background than charter members.

That’s fine. For better or worse and probably both, the landscape of collegiate sports has changed. Texas no longer plays Arkansas every year; Oklahoma no longer plays Nebraska. Conference realignment is the bell that cannot be un-rung, and realignment is what led the ACC to the Barclays Center, hard by the Brooklyn Bridge.

All those Big East alums — mostly Syracuse, but also Boston College and Miami and Notre Dame and Pitt and even Louisville — had grown accustomed to March in Manhattan. Can you hope to keep them down on the tobacco farm once they’ve heard the siren song of Broadway? From the moment the ACC began its latest round of poaching, moving the league tournament to NYC was a fait accompli — if for no reason other than to nip Jim Boeheim’s whining in the bud.

Sure enough, the ACC awarded its showcase to Brooklyn for 2017 and 2018. That’s also OK. It was worth trying once, maybe twice. It’s not worth doing as a matter of course.

I have nothing against New York City. I like visiting. To borrow from John Mellencamp, I’m hayseed enough to say, “Look who’s in the big town.” (Example: I’ve walked past Christine Baranski and Tony Roberts — feel free to consult IMBD — on Broadway.) Some of my friends in the New York media felt strongly that the ACC needed to establish a footprint in the Big Apple. I respectfully disagree.

The ACC is used to being the biggest dog in any city where it convenes. (Granted, Greensboro isn’t all that big.) The ACC plays the best basketball and has for 50 years. The ACC doesn’t need New York’s validation, and here’s the real incongruity: Its tournament isn’t being staged on or just off Broadway. It’s playing ball across the bridge.

Brooklyn has become a Happenin’ Place, or so I read in the Times. It’s less hoity-toity than Manhattan and therefore offers greater boho chic. “The Americans” — the best show on TV; Season 5 premiered Tuesday night — shoots in Brooklyn. Its stars (real-life couple Keri Russell and Matthew Rhys) live in Brooklyn. If I walk past either on Flatbush Avenue, I’ll let you know.

But the ACC couldn’t book the world’s most famous arena because Madison Square Garden has been claimed by what’s left of the Big East. The ACC doesn’t get to play off 33rd St. and 7th Ave. It’s playing in an arena that features championship banners won by the Nets when they were members of the ABA and the Islanders when they were based in Uniondale, which is a ways from here. (There’s also a banner saluting Jay-Z, who owns the Nets, who are terrible.)

Brooklyn may be a hipster haven, but it doesn’t carry the cachet of Manhattan. Even if it did, that doesn’t mean the ACC should be here beyond 2018. The heart of the ACC remains in North Carolina, but that’s also a tangled issue. Owing to House Bill 2, better known as the bathroom-rights bill, the conference could well pull its 2019 tournament from Greensboro and 2020 from Charlotte. (The league already relocated its football championship from Charlotte to Orlando.)

So: If you can’t play in North Carolina and aren’t crazy about Brooklyn, where’s a better alternative? Tampa? (Errr … maybe.) Washington D.C. with Maryland no longer around? (Nope.) Greenville, S.C.? (Whoa, Nellie.) Atlanta? (We have a winner!)

I’m guessing the backlash from old-school ACC fans — as opposed to the rights-holding ESPN, which loves this area and surely thirsts to make the ACC title tilt a lead-in to yet another Yankees-Red Sox exhibition game — will be severe. If you’re coming to the games in Brooklyn and staying in Brooklyn, you’re paying a fortune and dealing with awful traffic. (Yes, they do have subways.) If you’re coming to the games in Brooklyn and staying in Manhattan, you’re paying twice that much and having to cross a bridge to boot.

I’m guessing the ACC will think hard about coming back here after 2018. I cannot imagine this becoming a semi-permanent home. The ACC is strong enough — it plays really good football, too — that it doesn’t need to kowtow to any city, not even our biggest.

For the record, this event was one game old when the first dissent was sounded. Asked how he liked the setting, Clemson’s Shelton Mitchell said: “I’ll be honest. I was kind of disappointed. I grew up in North Carolina. I’m just used to always seeing the ACC tournament in Greensboro.”