It’s 3,500 Miles From Philadelphia. But for Eagles Fans, It Feels Like Home.

Benjamin Franklin, the consummate colonial wanderer, once observed that home was not just a place, or a thing, or a food. “A house is not a home,” he said, “unless it contains fire for the mind, as well as the body.”

Centuries later, J.P. Teti, Philadelphia’s own accidental ambassador to England, has learned this, too: A city — nay, a people — cannot survive on cheesesteak alone.

If the seat of American power in London resides at the embassy, a good chunk of its spirit can be found on Cleveland Street in central London, sandwiched between traditional British architecture, in the shape of a gritty Philly dive bar: Passyunk Avenue, named for South Philly’s famous thoroughfare.

To step inside is to be transported. Pendants from Philadelphia schools frame the windows; T-shirts and jerseys hang from the rafters. Dollar bills with scribbled signatures paper the walls. Among London’s many manufactured American bars, Passyunk Avenue stands apart for the simple fact that it isn’t a gimmick.

The brainchild of Mr. Teti, the bar is a Mecca of sorts for American sports fans far from home. Cozy, raucous and drawing heavily from Philly’s (in)famous sports obsession, Passyunk Avenue caters to nearly anyone hoping to watch mainstream American sports. But it has cornered one emerging market: the N.F.L., which is surging in popularity among international audiences. Commissioner Roger Goodell has said he is hopeful that the league might expand abroad and, someday, even see a Super Bowl played in Europe.

Such lofty aspirations, though, feel eons away from the comfortable perch of a Passyunk Avenue bar stool this week, days before the Philadelphia Eagles march into a championship rematch with the Kansas City Chiefs. Sitting among tchotchkes and trophies, it’s not really about football, or cheesesteaks. It’s never really been about any of that.

‘We’re not a sports bar. We’re a dive bar.’

Mr. Teti remembers exactly where he was in January 2018, just before Philadelphia’s last (and first) Super Bowl victory: sore and despondent under a rail arch in southeastern London, packing up his fledgling cheesesteak truck for good.

The truck had been a brief experiment for Mr. Teti, who grew up split between Southern New Jersey and South Philly, where he had a gaggle of Italian cousins, before moving to London for work. Convinced he could win the city over, he walked away from his corporate job in 2016 on the gamble that Brits might come around to the gloppy appeal of Philadelphia’s famed sandwich.

But slinging steaks out of a trailer hadn’t fostered the community Mr. Teti had hoped for.

“This isn’t what I imagined,” he recalled thinking at the time. “I want to move it away from being cheesesteaks. We’re going to create a cultural outpost in the form of a Philly dive bar.”

Despite the many pubs in central London, an authentic dive couldn’t feel farther. That hasn’t stopped plenty of pubs from trying, but the efforts often feel like a Disneyland American Legion. Lost are the time-tested details, only missed once they’re an ocean away: Flickering neon. Football in the background. Gummy stools and brash takes from chatty strangers.

These small touches are taken seriously in Philadelphia, where dive bar culture predates the country itself, and words like “grit” and “grime” are less disparagements than badges of honor. (An Atlantic City bar once sued Philadelphia magazine after a reviewer called it a “dive.” According to the magazine’s editor: “This is a case of a place that can’t take a compliment.”)

At the risk of dumping tea in the proverbial harbor: Pub culture just isn’t the same.

With a renewed sense of purpose, Mr. Teti rented a space in the Fitzrovia neighborhood of London and opened its doors in March 2018. The business, known as Liberty Cheesesteak Company when it was run out of a truck, was rebranded as Passyunk Avenue after South Philly’s main artery, where Rocky Balboa trained and where Pat’s and Geno’s (overrated) cheesesteak houses still wage their generational war. Mr. Teti had bought the name as a website domain on a whim years before.

“I’m not selling cheesesteaks. It’s always been about, for me, sharing the cultural inheritance that made my upbringing special,” Mr. Teti said, hunched at a wooden table at Passyunk Avenue’s Fitzrovia location. It is now one of three — soon to be four — locations, all of which have waiting lists hundreds deep for Sunday’s game, despite the 11:30 p.m. local kickoff time. This Super Bowl is a lot different here, now, than it was in 2018.

“It really shouldn’t have survived six months,” Mr. Teti said of his bar, chuckling. “But it did.”

‘This is Philly, through and through’

Passyunk Avenue is not just about cheesesteaks, and, as Mr. Teti and any lifelong, righteously bitter Philadelphia fan would tell you, the Eagles aren’t just about football. The Lombardi is more Holy Grail than trophy, the end of what can only be described as a torturous emotional pilgrimage. Indeed, the Eagles are less pastime than religion, as inherent to the city’s collective identity as Benjamin Franklin, as soul music, as a citywide served from a scratched-up counter on Two Street.

Mr. Teti’s bar is a dutiful disciple. It hoards late-night licenses to solve the time difference problem for after-hours American games. The bar found a Dutch butcher who can slice the steak the right way, and developed its own Whiz when British food codes wouldn’t let the real(?) stuff in.

“This is a very specific Americana, you know what I mean?” said Jessi Riley, a South Jersey native and head of culture for the franchise. “This is Philly, through and through.”

Passyunk Avenue has star-studded bona fides. The Kelce brothers, including the retired Eagles center Jason, once recorded their popular “New Heights” podcast from the bar. The Phillies manager, Rob Thomson, stopped by to pull pints when the team played a series in London last year. Brent Celek, the retired Eagles tight end, once partied there with the Lombardi Trophy.

But Passyunk Avenue’s real credentials are its walls, with not a bare inch in sight. It is a sea of the familiar: Scribbled messages like “DELCO” or “Wooder from the crick,” in homage to Philly’s famously tricky accent. A South Jersey marching band jacket. A reusable Wawa shopping bag, perfectly crumpled as if pulled from a back seat and tacked to the wall.

(One intoxicated chancer once made off with what, to an outsider, probably appeared to be an innocuous prop: a stuffed Eagle head. It was, in fact, the donated costume head of Swoop, the official Eagles mascot. Internationally vilified by Philadelphia fans online, the mortified man returned the head, unharmed, the next day.)

Every piece of décor, Ms. Riley said, was donated, often from patrons so moved by the feeling that they took a jersey right off their backs at the bar.

“I’ve worked in several museums,” said Ms. Riley, a historian by trade. “I feel like I purvey more culture in this place than I ever did in any museum I ever worked in.”

‘Go Birds’

I wandered into Passyunk Avenue for the first time on the Tuesday before the Super Bowl, gloomy and pining for Philly’s riotous week. I left the city years ago but have trekked back regularly to watch big games with my brother. Stymied by an ocean, we’ll spend this Super Bowl apart.

Home is not a cheesesteak, or even a football team. Instead, I found it in this Fitzrovia dive’s subtleties, reserved only for those who know to look: The gentle stretch of an “o,” that turns it into “owh.” The casual “yo,” as punctuation and parting. The soft “shh” that Mr. Teti adds to the second syllable of “Passyunk.”

This is bone deep, for anyone who has ever left a place they love.

Ms. Riley will watch Sunday’s game in the same ’90s Starter team jacket she has had for decades — she pulls it off a chair and displays the internal name tag, still bearing the echo of a childhood scribble. Mr. Teti will be at the Leake Street tunnel, near Passyunk Avenue’s Battersea location. There, they’ve arranged for a tailgate-style party, in homage to the pregame scene at Lincoln Financial Field, the Eagles’ home stadium.

At the bar, we steer away from predictions, wary of jinxes. I’ll be back for a cheesesteak soon, I pledge, pressing the door forward into the gray London chill.

“Go birds,” I say over my shoulder.

Behind me, a familiar, parting chorus: Go birds.