As fans awaited the beginning of a Korean pop concert on a summer night at Madison Square Garden, concert promoters played a video on proper etiquette. Screaming or jumping around too much, it warned, could ruin the show for others.

The video had no effect. The screams from U.S. fans never stopped or dulled in intensity as Seventeen, one of the top bands in South Korea and around the world, performed for the first time at MSG. The teenage girl next to me screamed hoarsely at the band (and into my ear), “I love you!” as she filmed with her smartphone in one hand and grasped a light stick indicating her band allegiance with the other.

Seventeen showcased the magic that pulls people into Korean pop music: effortless choreography, sugary bops, and cool fashion. The crowd was young and ethnically diverse: Asian, white, Hispanic, Arab, black, and Orthodox Jewish. Many of those I met were from the Midwest and had traveled to New York for a rare chance to see their favorite Korean bands.

“It’s a good exposure to a different culture,” said Caitlin Quirk from Cleveland, Ohio, who was on her way into the Seventeen concert with her somewhat reluctant mother and a friend, Angela Sciarappa. K-pop songs are mostly sung in Korean, sometimes with English sprinkled in, and Quirk and Sciarappa, who are in their 20s, said they have learned some Korean and can recognize “very small words” in songs now. “And, it’s just really fun,” added Sciarappa.

The concert was the culmination of KCON New York, a convention for Korean culture with a focus on pop music. (K-pop technically refers to bubblegum pop bands, but can be shorthand for any Korean music.) When KCON held its first East Coast convention just outside New York in 2015, it had 17,000 attendees. This year it drew 55,000, having grown so fast that the Korean entertainment company organizing it had to change locations this year to host the dance competitions, concerts, and panels in the cavernous Javits Center in Midtown Manhattan and Madison Square Garden.

“Just a few years ago, it was almost unheard of to sell 5,000-plus tickets for a K-pop show in North America,” Derek Lee, CEO of K-pop promoter SubKulture Entertainment, recently told Forbes. “However, it now happens with regularity.”

The so-called Korean Wave (often known as Hallyu) has swept ashore all over the world, from Iraq to Indonesia. Korean television dramas are the rage in China, and Korean pop dominates music charts in Thailand. Algerian fans have begun incorporating Korean into their everyday speech and text messages. But the United States has been slow to catch on. That appears to be changing now, thanks to social media and to American pop culture’s increasingly global tastes.

Most teens and young adults I interviewed at MSG had discovered K-pop through YouTube or other social media, bypassing U.S. entertainment companies and public relations machines. Venus Nguyen, a 16-year-old from Massachusetts, said she followed her sister into the world of K-pop primarily through YouTube and Twitter. It was Venus’ first time at KCON, and she said she’d made real-life friends through their shared love of Korean pop culture.

“[American] media is confused why it’s so popular,” laughed Nick Gabriel, 23, who came to the K-pop show at MSG from his home in Long Island, along with two of his cousins. Sarah Gabriel, 16, offered evidence of how deeply Korean music has penetrated Long Island: Her parents know about BTS, the Korean pop band that has drawn comparison to the Beatles and that (like the Beatles and the Monkees) charted three No. 1 albums in less than a year.

As Korean pop culture gains a stronger foothold in the United States, longtime Korean culture watchers have ideas on the good and bad trends it could bring to the United States. Among the good things: It introduces Americans to a new culture that tends to be less sexualized and violent than American pop culture. Among the bad things: K-pop comes with a fandom beyond even that of American pop culture. The extreme fandom can make both fans and their pop idols miserable, showcased in some high-profile suicides of Korean celebrities.

Outside of Madison Square Garden before the Seventeen concert, the new K-pop fans swarmed. A gaggle of cameras appeared and began clicking away as a swank band made up of Korean teens—in high fashion and with perfect hair styling—walked down the sidewalk and into the arena. People on the street began screaming and running toward them with their phone cameras on, but the serious K-pop fans I was interviewing nearby immediately knew this band wasn’t famous and gave it no notice. The group turned out to be a band in training that would be introduced at MSG later that evening.

Despite the screaming during the concert, the American teenagers I interviewed outside MSG weren’t rabid. They seemed like normal fans. They liked the positive themes of K-pop and the high-quality, story-based Korean music videos. They didn’t care about the language barrier, and they were drawn into Korean entertainment companies’ masterful use of social media, where bands stream their dance practices or trips to get takeout food.

The teenagers’ parents liked that the stars don’t swear. As a country with a significant Christian population, Korea tends to be more culturally conservative. The conservatism of Korean pop culture is perhaps why it appeals to so many countries internationally, and why I saw Muslims and Orthodox Jews attending the KCON concert.

Journalist Jason Yu has covered the Korean pop culture industry for a decade in Korea and the United States. He said Korean pop music has become more sexualized, but Korean television has recently banned a slew of music videos it deemed overly sexual. Korean television dramas still eschew violence, sex, and bad language.

Korean celebrities are also much more comfortable embracing a Christian identity than their American counterparts are. K-pop bands will perform worship songs at shows or show up to perform or lead prayer at megachurch worship services. Yu said some celebrities purposefully emphasize their faith because it communicates to audiences that they’re pure and serve the community.

“To a Korean it’s a bonus point,” he said.

Going to concerts and doing interviews and sitting through auditions, Yu has had a front-row seat in the industry as the K-wave hit the globe. In the late 2000s, he recalled, the Korean entertainment company JYP tried to break into the U.S. market. JYP sent its band Wonder Girls, hugely popular in Korea at the time, on a 45-day tour with the Jonas Brothers. But Wonder Girls didn’t take off here.

“The American public wasn’t ready,” Yu said. “[JYP] was 10 years too early.”