LOS ANGELES — There’s no doubt that K-pop broke through in the United States in 2018.

After years of slow advancement in coastal capitals like Los Angeles and New York, the sleek yet busy sound from South Korea finally reached a mainstream American audience last year thanks to BTS, the seven-member boy band that became the first K-pop group to land an album at No.1 on the Billboard 200 — then did it again with another record just a few months later.

But what happens after a breakthrough? That’s the question K-pop is poised to answer in 2019, as some of its biggest stars take up positions in this country’s musical institutions.

On April 13, BTS will notch another first for K-pop when it performs on “Saturday Night Live,” one day after the release of its highly anticipated album “Map of the Soul: Persona.”

That same weekend, Blackpink — a female foursome from Seoul heard last year in a collaborative single with Dua Lipa — will become the first K-pop girl group to play the Coachella Valley Music and Arts Festival in Indio, California.

What these bookings indicate is the beginning of the second phase of K-pop’s American adventure, in which the music answers its embrace by opening itself up to influences from its new surroundings.

K-pop was shaped from the start by Western sounds. During an interview with BTS last year, the group’s leader, RM, was quick to acknowledge the importance of acts like the Backstreet Boys. The way he sees it, BTS is “re-exporting” the classic boy-band style “to the rest of the world where we had initially drawn much of our inspiration,” RM said.

But much of K-pop’s appeal lies in the way it diverges from that blueprint — in the bold collision of rhythms and textures that defines a song like BTS’ “Fake Love,” for instance, which has a chaotic energy nobody ever got from ‘N Sync.

The music’s thrillingly fluid ideas about gender also have distinguished many K-pop acts from their American counterparts. In September at Staples Center in Los Angeles, where BTS played four sold-out concerts, the group’s frilly costumes and sensual moves reflected pretty evolved thinking about pop-star masculinity.

Yet American pop has a way of streamlining what it absorbs. You can hear that in Tomorrow x Together, a young quintet assembled by Big Hit Entertainment, the successful Korean company behind BTS.

On its debut EP, which came out in March ahead of an expected trip to the U.S. in the spring, the boy band echoes Justin Bieber and Boyz II Men; it’s as sonically detailed as the most ambitious K-pop) but also feels newly geared to American tastes — one reason that Republic Records, home to Taylor Swift and Ariana Grande, has signed on to promote the group in the States.

It’s unclear to what extent BTS, which will support its upcoming album with a stadium tour, has allowed its music to creep our way; Big Hit is keeping “Map of the Soul” tightly under wraps.

Might the group try singing in English? RM seemed wary of the idea in last year's interview, describing BTS’ Korean lyrics as a core feature of its music.

But anyone tracking K-pop’s crossover knows that, for all its success on social media and on streaming platforms like Spotify, the style has yet to gain a foothold on Top 40 radio, at least in part because of that language barrier. (Yes, “Despacito” demonstrated that American programmers are willing to spin a song not sung in English. But they haven’t jumped on one like that since.)

In its email, Blackpink acknowledged as much. Airplay in this country is “definitely important,” it said, because it “allows us to introduce our music to new fans.”