The World Cup returned to U.S. soil on Friday after more than three decades, as passionate American fans — wrapped in flags and wearing red-white-and-blue costumes — and a small but boisterous section of Paraguay supporters packed the SoFi Stadium in Inglewood, Calif.

Many of them beat the notorious Los Angeles traffic by arriving five hours early at the venue, renamed Los Angeles Stadium for the tournament. Some were even there before the teams, enjoying beers and watching the Paraguay players file into their locker room on a large screen.

The excitement began early in the day with an indelible Los Angeles image, if there was one. Local television aired footage from a helicopter of the American team bus cruising on the freeway from its training center in Orange County toward the city.

The game arrived against a backdrop of continental disunity, fears about U.S. immigration actions and anger over sky-high ticket prices. But as kickoff approached between the United States and Paraguay, it all seemed to melt into joy.

Fans from around the world are gathering in Los Angeles for the World Cup. People from 195 countries have purchased tickets to games in the city, according to Vanessa Kromer, the head of communications for SoFi Stadium.

On Friday, there was an international flavor to the party, with fans not only celebrating the United States and Paraguay but also many other countries.

Juan Carlos Muñoz, an Angeleno draped in a bright yellow jersey of Colombia, his homeland, arrived early.

He was by himself but said, pointing skyward, that he felt his father’s presence. “Soccer is what connected me to him,” said Mr. Muñoz, 64.

Juan Martinez, a lifelong soccer fan, said he couldn’t sleep the night before the game, his first at a World Cup.

“I was so excited,” said Mr. Martinez, 55, who was born in Mexico and has lived in the Los Angeles area for 35 years.

Walking into the stadium, wearing a U.S. jersey, he said, felt “surreal.”

The “U.S.A.!” chants from the home fans were deafening, but there was also a sizable Paraguay contingent.

Mauricio Valenzuela, 42, lives in Florida, but was born in Asunción, the capital of Paraguay. Until Friday, Mr. Valenzuela said he had yet to see Paraguay play in a World Cup match or in the United States.

“That’s why we had to come,” he said.

Before the game, an American fan ribbed Mr. Valenzuela, saying he hadn’t seen any Paraguayan fans in the stadium.

“We’re coming,” Mr. Valenzuela said, pointing to a throng of Paraguay fans streaming into the stadium.

The excitement was hardly limited to the venue. Across the Los Angeles area, fans gathered at bars, restaurants and watch parties. Miles away from the match, dozens of soccer fans packed into the Thirsty Crow, a bar in the Silver Lake neighborhood of Los Angeles.

Surprisingly for the city, where fans even leave a Dodgers World Series game early to beat the traffic, the stands at SoFi Stadium appeared full until the end, even with the U.S. team comfortable and cruising.

The fans that arrived hours early had avoided bad traffic, but they got a flavor of Southern California after the match as cars and trucks bottlenecked the roads out of Inglewood.