U.S. fans have traveled by the thousands to the World Cup in Brazil. The U.S. team plays Portugal in an important group match on Sunday. (Vassil Donev/EPA)

With the World Cup circled on the calendar, the Brennan family passed on big splurges, skipped family vacations and saved money for four years. This month the five of them traveled nearly 4,000 miles from their Fairfax home, finally sinking their toes in the white beach sand of Natal, a city on Brazil’s northern coast. They had a look around, soaked in the postcard scenery and couldn’t believe how close they still felt to home.

“It was just like being in Fairfax — Americans everywhere,” said Rick Brennan, who works in marketing. “We’d go to restaurants and it was all U.S. fans.”

Thousands of Americans have converged on the Amazon this weekend, determined to inject their brand of red, white and blue fandom into a nation that’s not exactly lacking in sporting passion.

“We’re kind of in the heart of soccer [in Brazil],” said Harry Spritzer, a Seattle native who traveled to Brazil for the tournament.

The United States will take on Portugal in its second World Cup match Sunday in Manaus, and the 40,000-seat Arena Amazonia will feature plenty of loud Brazilians, clad in green and yellow and cheering for Portugal, with whom they share a common language and heritage. But there surely will be a strong American contingent on-hand, too, eager to see the U.S. team advance past the tournament’s group stage.

According to FIFA, more than 200,000 World Cup tickets were purchased by U.S. residents. The only country responsible for more ticket sales is the host nation. While soccer fans from all over the world can be spotted across Brazil, most wearing their patriotism on their sleeves — and often their heads, backs and legs — the Americans have been particularly ever-present, from Natal’s beaches to Rio de Janeiro’s favelas.

Where the U.S. team goes, its fan base travels. Fans reported that a flight from Sao Paulo to Natal last week had so many Americans on board, pilots had to delay takeoff because there weren’t enough Portuguese speakers sitting in the emergency row.

Americans were both vocal and visible at the United States’ first match of the tournament, a 2-1 victory over Ghana last week. American midfielder Kyle Beckerman, a Crofton native who graduated from Arundel High, said it was “almost feeling like a home game.”

“As players, we can’t ask for anything more,” teammate Michael Bradley said. “When we are standing on the field in Natal before the game against Ghana and the entire stadium is singing the national anthem, you get goose bumps. It’s what you dream of — playing in a World Cup in a stadium full of American fans. And to have that stadium be in Brazil but still full of American fans is pretty special.”

After the Ghana match, at 2:30 in the morning, the new Natal airport was flooded with American fans heading to their next destination: Rio for some, Sao Paulo for others. Fans were napping on the floor and crowded in line behind the only open concession stand, all decorated in red, white and blue.

“I think it’s testament to our culture,” said Megan Mendoza, 32, from Yakima, Wash. “Our soccer culture is growing.”

With 32 nations competing for global bragging rights, the World Cup manages to toss every nationality, ethnicity, religion and background into a big pot and stir them around. They sit side-by-side in Sao Paulo cafes and Salvador bars, watching matches together, belting out national anthems and pausing only to order a new round of drinks.

“It’s awesome,” said Jeff Michel, 24, an accountant from Chicago. “You see every country, everyone so dedicated to their team. Americans can relate to that.”

“Overall, my safety is never in question, through any of the fan fests or the games I’ve been at,” said his friend Roberto Marquez. “And it’s been exciting. It’s a melting pot of different cultures here, and it’s unbelievable.”

Though the United States lacks the rich soccer history of many nations, four years ago the Americans also accounted for the highest number of ticket sales outside the host nation. FIFA reported 130,000 tickets to South Africa’s World Cup were purchased in the United States.

“Our per-capita GDP is higher. It’s easier to travel. It’s closer to us than previous World Cups,” said Tyler Chisholm, a 32-year-old doctor, of the increased tickets sales to the event in Brazil. “But I think there’s a lot more American fans in the United States than there used to be.”

The bandana-clad members of the American Outlaws fan group have been particularly visible in Brazil. Back home, the rowdy fan group has about 18,000 members nationwide and added its 141st and 142nd chapters last week, in New Haven, Conn., and Topeka, Kan. Most chapters in the states have organized viewing parties for each U.S. game.

More than 500 of the American Outlaws fans are traveling together to each of the three U.S. games in the group stage, documenting their journey on the Web site ­AOinBrazil.com. They’ve organized parties in each host city the night before games and another for the hours leading up to each match.

Even though the United States entered the tournament with a difficult draw and relatively low expectations, traveling to the World Cup isn’t just about wins and losses for fans.

“The chances of the U.S. team are slim to none, right?” said Luke Culley, an accountant from Chicago who made the trip to Brazil. “If they win, oh my God, it will be the best thing in my life. . . . It would just be huge.”

Four years ago, right about the time Rick and Michelle Brennan left the World Cup in South Africa, the couple came up with the plan. When the 2014 Cup rolled around, they would take their three children along for the adventure.

Michelle set up a new savings account. To ensure the account would grow steadily, she immediately limited Rick’s access. Every week $100 went toward the trip, and in time, flights were booked, hotel reservations made, game tickets purchased. The children had a paper chain taped to the wall of their home, and each day they would tear off a link.

Snow days extended the Fairfax school year, which presented a slight dilemma. The Brennans couldn’t exactly push back the World Cup, so the kids’ school year ended nine days early.

“We figured they’d learn a lot more from this than whatever they’d do those last nine days,” Rick said.

Soon, suitcases were crammed full, a patchwork of red, white and blue: canvas sneakers, pants, jerseys, flags. Not long after landing in Brazil, 14-year-old Connor was playing in an impromptu beach soccer game, 10-year-old Rory visited the world’s largest cashew nut tree and 6-year-old Donovan was wearing a Captain America mask, ready to take in his first World Cup match.

“It’s all been great so far,” Rick said. “We’re already making plans for the next World Cup in Russia."

Dom Phillips, in Salvador, Brazil, and Steven Goff contributed to this report.