You take your shoes off at the door because that's what your family did. You wave with the palm out instead of curling your fingers. You don't pour your own glass first at dinner. You stand for the national anthem. You know which fork is for salad. Nobody taught you these things in a class. They were absorbed.
K's claim is that what you call "who I am" is mostly absorption. The body learned the gestures. The mouth learned the responses. The mind learned which questions are askable and which aren't. You inherited a culture and then started introducing yourself with it. I'm Korean. I'm Texan. I'm Catholic. Each phrase a small confession that you are quoting your ancestors.
Culture is the costume you can't see because everyone around you wears the same one. The American doesn't notice American-ness. The fish doesn't notice the water. K's whole project was making the water visible — turning what felt like this is just how things are into this is what was handed to you, and you can put it down.
There's a particular discomfort when culture gets named as culture. The person told their accent is regional, their etiquette is class-specific, their tastes are demographically predictable — feels reduced. Smaller. The "I" had thought it was authoring those things. Now it learns it was reciting them.
Culture isn't bad. The shoes off at the door, the bless-you, the waving palm — all fine. The problem starts when the inheritance gets mistaken for the inheritor.