A common social phenomenon is that a term will get washed down by misuse, until it loses its meaning. Not every angry woman is a Karen.
A Karen is an entitled (usually white) woman who acts like the main character in her own movie, asserting her rights while clearly trampling on the rights of others. The usually white part matters, because white women have oppressed other people — notably Black men — while claiming their rights.
As a trans woman, I had my own encounter with a Karen in a public restroom at a Regal movie theater, back in 2018. I had finished peeing and was washing my hands. My partner, a five-foot-tall Chinese-American nonbinary person, was with me, and we were chatting away. (I took for granted they always came with me when I used a public restroom. It was years before I realized they did that because they were protective of me).