The Pirates, who celebrated their 10th anniversary this past November, were initially regarded as oddballs at East River, which is decidedly not a sports bar, unless you count billiards or biking. Out front, there’s a sign featuring an enormous gear and a vending machine selling spare inner tubes. The backyard has communal grills for customer barbecues in warm weather. The inside is sparsely decorated, and being a classic dive, contains only a couple of tiny televisions that are always on but no one pays much attention to. A regular game day will bring a mix of bike punks, New York soccer heads, and Germans on a pilgrimage to watch St. Pauli on a giant projector screen instead.

Ms. Roggenkamp, who works for the auction house Christie’s, was introduced to the cult of St. Pauli about five years ago when she was studying German through a private program. A classmate took her to watch a game at East River. Over the next year and a half, she slowly started to take on a leadership role in the supporters’ club. In keeping with the team’s philosophy, that typically involves passing a collection cup for charity during halftime. The ritual takes on an air of communion — a characterization that Ms. Roggenkamp agrees with.

“I was having a conversation about it with one of my friends the other day,” she said. “And he was like, ‘You talk about this as if it’s your church group.’”

Jah Jah Brown, half of the Brooklyn-based rap duo known as Ninjasonik, has been coming to watch games at East River Bar for the past six years because he’s enamored with the team’s politics. He said that German tourists regularly walk into the bar, which is typically full of bicycles, and have to ask, “Are we in the right spot?”

In fact, the bar is a bridge between the two nations. Mr. Paranya remembered being with a Turkish friend years ago and lamenting that he didn’t have a geographical allegiance to a soccer team as an American. The friend immediately pegged him as a would-be St. Pauli fan, though the comment was initially forgotten. Years later, he and his wife popped into East River Bar for a beer, where a game happened to be screening. After about five minutes, he realized who was playing. “I remembered that I was supposed to like these guys,” Mr. Paranya said. “By the end of the game I was singing all the songs and had purchased a T-shirt.” A few years later, he took a trip to Germany, which he described as a pretense to visit St. Pauli’s stadium. He wore his supporters shirt and made about “20 new best friends,” some of which he now sees occasionally when they come to visit the United States and make their obligatory trip to Williamsburg.

With about 10 minutes left in the game that Tuesday, the other team scored, though not many fans seemed to notice. When they sunk another goal and things seemed good and over, one of the Pirates’ organizers, Sören Thode, switched the broadcast to a YouTube video of the German entertainer Hans Albers’s ode about the Reeperbahn — the red-light district district of working-class Hamburg. People finished their beers and said their goodbyes until the next match on Monday afternoon, though they, of course, wouldn’t be watching until nightfall.