they are not mainstream but there is always huge support for Kpop acts besides the obvious, BlackPink and BTS.
not even need to be Twice level but even less popular groups than twice get attention more than some western acts. for example aespa is a rookie and is not one of the top groups but i was baffled they had many fancams with crazy screaming fans in their Coachella performance. they announced their participation in three days yet they immediately got enough kpop stans ready to support. the 88rising set and other local acts before them that werent kpop were not comparable in reception. the moment it is a kpop group it gets hyped.
another rookie group like ateez got very well received when they went to the states. it just feel like if you have an event and invited a mediocre to semi popular western act with any kpop group, the kpop group would be the main event. if that's not the popularity of kpop i don't know what is.